Watering/Feeding Indoor Mounted Cattleya Seedling

[galguibra]

First time posting on here after recently getting my fist ever orchid!! I took a look through the guide, but feel free to let me know about any norms I might've missed or if I went into too much detail. I wanted to make sure there was enough detail that people could confidently weigh in without needing too much immediate expansion/clarification, but I realize this turned into a bit of a full-length thesis along the way . Thanks in advance for any advice you all can provide!

TLDR, I'm new to orchids and was hoping to get some guidance on watering and feeding a mounted Cattleya seedling I just got earlier this week, but here's a full context breakdown in case it helps:

Specimen: Cattleya intermedia v. aquinii fma. coerulea

Seller: Louisiana Orchid Connection, link here

Size/Age: Came in a 2" net pot, but was definitely outgrowing it. Roots had already come out through the bottom and sides into the cache pot. Not sure how old it is exactly. See picture below for how it looked on arrival:

Mount: Cork bark flat, ~14"x5" average dimensions. Attached bare root and inverted using 2mm rubber-coated floral wire, and nestled into a slight hollow in the mount. I tried to position the new growth so it could climb up the mount, but I also wanted make sure everything could drip dry as easily as possible and keep water from getting trapped anywhere and causing rot. See pictures below (very recently watered in both images):

Full View:


Close-Up:

Growing Conditions: Hanging on the wall in my bedroom near an automated cool-mist humidifier and some other tropical plants, far away from any vents.

Humidity: The humidifier is set to keep the humidity between ~60%-65%, although it sometimes drops to ~50%-55% if the AC is running particularly hard due to the weather. Peak output is ~300mL/h, but it'll adjust as needed.

Airflow: I have an air circulator running 24/7 rated at ~512 CFM. Room volume is about ~1161 cubic feet, so it should do the whole room in a little over two minutes. I have the fan on a bookcase pointed up at the ceiling corner behind all the plants, so the air comes down and around to give them a gentle breeze. You can feel it, but even the thinnest leaves on any of the plants only just barely sway.

Temperature: It's starting to get pretty hot in Chicago, but I still wanted a nighttime temperature drop for the plants, so my HVAC is set to 73°F during the day and 68°F at night. The central fan also circulates air for 15 minutes every hour just to keep things fresh.

Lighting: I have the mount under a full-spectrum (380nm - 800nm, 6500K) LED grow light, and it's calibrated to run at ~200 PPFD on a 12h/12h timer—the same schedule as the HVAC. DLI comes out to ~8.5, and the lamp doesn't give off any noticeable heat at all. It's still like 16" away since I wanted to take it slow on a new plant, but I can definitely up the light as it grows!

Everything above I took as a starting point based on experience with other (sub)tropicals, so hopefully that makes it easier to advise on watering and feeding, which are the main things I'm really unsure about. That being said, any feedback on the growing conditions and stuff is also very welcome!

Also, I should note that when I unpotted the seedling, I did find a millipede in the bark chips. I wasn't sure if it was the detritivorous or herbivorous kind, but probably not a good sign either way. There wasn't any obvious damage to my untrained eye, but just to be safe I gave the roots a quick dip in 0.75% hydrogen peroxide to help clean them off without risking too much oxidative stress. This is also part of why I chose to mount bare root, in case anything else came up and needed quick attending to. See below for a picture of the unwelcome guest:

All of that out of the way, this is what I've been trying so far:

Water: I spray with distilled water at room temperature whenever I see that the velamen is looking thoroughly silver/white, and that the leaves and the base of the plant near the rhizome have had a chance to just dry off. This has been maybe ~5x a day so far, and I spray until the roots are green all over and the mount is lightly dripping.

I chose not to mount with sphagnum so I could keep an eye on the roots and give them lots of air, but I might add some if the watering burden gets to be too much or if I need to be away for a weekend or something. I tend to be a bit of an overwaterer and I know that's extra problematic with orchids, so I figured bare root might be safer for me unless in turns out the seedling really can't handle it.

Fertilizer: I didn't really want to be regularly soaking the whole mount if I didn't have to—although I did give it one thorough soak before actually mounting the seedling just so there'd be a little something to encourage growing onto new areas in the future—so I figured organic fertilizers applied as a spray might be easier to work with for now. Maybe I could do occasional soaks with inorganics once more of the mount is actually getting used? Open to feedback there for sure.

I also didn't want to go out and get specialty fertilizers for each of my different plants, so I've been mixing up nutrient solutions myself from component concentrates based on research I've done on each of my plants. My current approach is to feed once daily with a really dilute solution at ~25ppm N, with the rest of the concentrations coming directly from the manufacturer's directions for applying on orchids. I always pH the solution to 5.8-6.2 before applying, and only one watering per day has any fertilizer in it at all: the rest are all just plain distilled water. If it would be beneficial to buffer the water, I also have a seaweed extract that I could use on its own, as well as a 3-1-2 inorganic fertilizer with micronutrients, but I haven't used either on the orchid so far.

I've seen a lot of conflicting recommendations on fertilizers in particular (MSU vs K-Lite archetypes, dilute daily vs relatively stronger weekly feedings, etc), but for now I've been working off the concentrations for K-Lite as a starting point. This is what I have so far:

• Cal-Mag OAC (Organic Acid Complex), link here:
  

  
  

  • Concentrate is 4% available Ca and 1% available Mg (w/v)
    
  • Also has Fe, Mn, Zn, B, Cu, S
    
  • I dilute this one to 0.80mL/L, which comes out to ~32ppm Ca and ~8ppm Mg. This was the concentration given by the manufacturer for orchids specifically, but, for comparison, diluting K-lite to the same 25ppm N would give you ~20.83ppm Ca and ~6.25ppm Mg, which is pretty comparable but still definitely less concentrated.
    

  
  

• N-Primer (Slow-Release Large-Molecule Nitrogen Complex), link here:
  

  
  

  • 3.3% available N (w/v). 0.1% is ammoniacal, and the other 3.2% comes from other water-soluble organic complices
    
  • I dilute this one to 0.55mL/L, which gives me ~18ppm N, since there's also some coming from the next nutrient in the list
    

  
  

• Root Boost, link here:
  

  
  

  • This one is an organic C-P complex with liquid microbes/myccorhizae and a blend of "humic, fulvic, amino, and other organic acids complexed with extracts from 9 species of sea plants" (from manufacturer description). It has all kinds of natural plant hormones like you might find in seaweed sprays, plus all the other stuff listed. Plus it smells like chocolate!
    
  • The N-P-K is 1.4-3.2-0.7, and I dilute it to 0.50mL/L, which yields ~7ppm N, ~16ppm P, and ~3.5 ppm K. That rounds me out to the 25ppm N I'm shooting for, and is coincidentally also just under the manufacturer recomendation for orchids, which is ~0.53mL/L.
    
  • I confirmed with the manufacturer that this one doesn't have any auxins like IAA/IBA/NAA or any PGRs, since I saw on a forum somewhere that those can sometimes lead to deformities in orchids.
    

  
  

• Silica Gold, link here:
  

  
  

  • This one I only plan to use occasionally as a Si supplement, since it also adds an additional 1.3% (w/v) available K into the mix that I'm trying to avoid. It's a really cool formula though, and it also includes chalconoids, which stimulate synthesis of compounds that deter aphids/mites/etc; lots of amino acids and antioxidants; fulvic acid; and salicylic acid, which all help reduce stress, increase nutrient uptake and tolerance of drought, strengthen cell walls, etc. You can read a white paper on it here!
    
  • It has 3.0% (w/v) bioavailable Si in the form of silicic acid and other organosilicates, so I dilute it to 1.30mL/L, which is ~39ppm Si. This also adds ~16.9ppm K though, which why I'm only planning on applying maybe 1-2x/month.
    

  
  

So, to summarize all that, the fertilizer mix comes out to about 25ppm N, 16ppm P, 3.5ppm K, 32ppm Ca, and 8ppm Mg. For the 1-2x monthly that I plan to use the Si supplement, then I'd have 20.4ppm K instead on those days, plus the 39ppm Si. The distilled water itself has about ~10ppm TDS to start, and the rest of the micronutrient minerals in the Cal-Mag come out to ~0.896ppm, so in total we'd be looking at ~95ppm most days, and ~151ppm on the 1-2 days a month with the extra supplement.

Based on what I've seen researching online, it seems like a reasonable amount to me, especially since almost none of it is in the form of ionic salts and most everything is in some kind of organic complex or polymer. Would love to hear people's opinions on this mix/schedule though, since I realize it's not really standard. I try to apply it either early in the morning before the grow lights come on or shortly before they turn off for the night to maximize absorption and make sure the plant has time to dry off, which means the rest of the daily waterings should also flush any excess.

Thanks to anyone who's read this far in (I realize that was a lot of information all at once ), and I'm really excited to be starting my orchid journey with you all!