Baby orchids ailing, please help!

[irrka]

I have a few very tiny orchids i got a few months ago. They are under lights, with humidifier and fan. The rest of the orchids (that are much bigger) seem to be doing fine in the same setting except for the one leaf i burned against a lamp :facepalm:
However the little ones are definitely ailing. I've tried physan-ing the daylights out of them but that doesn't seem to have made much difference.

First pictures are Lc Melody Fair x Bonanza Queen
Second two: Dendrobium everlasting love
Last one Dendrobium tangerinum

i've never grown really tiny seedlings and since i was having trouble keeping up with their water needs, i'd left them in the sphagnum moss they came in.

[estación seca]

Physan in high doses may be toxic to Dens. It is certainly toxic to you. I strongly recommend never using fungicide unless you know for sure you have a fungus, you know what the fungus is, and you know that fungus is susceptible to that fungicide.

Problems with orchids are almost always due to growing conditions, not fungus. Think about the growing conditions before reaching for a fungice.

In the photos I see some of the medium looks as though it has been kept far too wet. Seedling should not dry completely, but neither should they be kept wet.

What are your growing conditions? Temperatures day/night? Humidity? How much light are they getting? How are you watering?

[irrka]

Physan: i have just used the concentration recommended and maybe every 4th watering or so.

They definitely get less water side much more than heavy watering side (the picture is just from being watered today). i end up watering when they are dry, but may forget sometimes since they're drying out much faster than i'm used to. They are the reason i put humidifier into the shelves hoping for a reprieve from heavy watering schedule.

I'm in seattle and don't really play around with the temps much; it's probably in the high 60s at night and mid 70s during the day these day? I have a lower hanging tube but it's LED for the babies, they get about 14 hours i think of light. the fan is running every other minute maybe? I've been trying to get the humidity up to 60s but mostly it's between 40s and 50s with the humidifier running

I can see how the Leilocat may be getting too dry and dessicated. Should i put it into a bigger pot? (i.e. more medium, dries out more slowly? idk....)
But the dendro spots?

[estación seca]

10-12 hours is enough light. 14 hours is more than they need. If you're struggling to keep them moist the light may be too close and too hot. I suggest you put a thermometer on the top of the pots to see what the temperature is. Orchid seedlings don't need as high light as adult plants might want.

Physan kills algae, plants. It is not a general preventative. It's a treatment for when problems exist. Using it every 4th watering could easily be toxic. Seedling plants are not nearly as tough as adults. I have lived in Seattle. I didn't grow orchids then, but I did grow other plants. I wouldn't expect orchids to get fungus inside the home unless in a tightly sealed enclosure with high humidity.

Tiny Lc. seedlings in moss from Seattle Orchids at your ambient temperatures should take 4-5 days to dry out. I suspect the problem is too much heat from the light plus the fan. If they're not in an enclosure you don't need a fan at all.

[skirincich]

Definitely do not use copper-based fungicides on the dendrobiums.

Fungus can be related to culture, but will a fungal infection disappear by just improving growing conditions?

I keep reminding myself that the key is growing good roots. Good luck!