leaf drop on phal with white fuzz on roots

[allyqat]

Hello everyone! Hope you and your orchids are having a good day Brace yourself for a long post and many needy questions

I bought a phal from a florist back in January and I've recently cut her spike back after blooming, hoping it might grow a new spike. She lives in my room about 6 feet from a partially shaded east window. One day, I noticed that the sphagnum moss she was growing in was turning black on the top and had a bit of a white frosted look to it - I'm not sure if it was a fungal growth or just nutrient deposition from the fertilizer I'd been giving her (MiracleGro water soluble orchid food which I belatedly realized has predominantly urea N and have bought new fertilizer - MSU orchid fertilizer, granular, tap water version). So I panicked and bought new media and locally I had MiracleGro Orchid Potting Mix Coarse Blend which has bark in it so I thought it might help with drainage (I live in Louisiana and thought it might be humid enough here, don't know).

Until her new pot (4" slotted orchid pot from repotme.com) arrived, I put her back into the flimsy plastic container she came in, with some 2 air slots I added on the side. I cut off roots I thought looked dried out and hollow, and dusted with cinnamon. I've been watering her more now, about every 2-4 days based on how long it takes the moisture haze to disappear on the inside of the clear container (used to water weekly in the sphag). She dropped her two lowest leaves (small leaves) and seemed ok. Then her next leaf started yellowing and fell off (pictured below, any idea what the weird circle hole near the base is?), and I'm all but certain she's going to drop two of her big leaves (due to yellowing at the base, pictured), leaving only two leaves. I'm worried I'm hurting her :-/ Should I get her a heating pad? If so, suggestions on what kind (I know nothing beyond their existence, haha)?

Most of her roots were beautiful shades of green when I took her out of the old sphagnum and now some of her roots are shriveled and gray (pictured below), thought seem to regain some vigor and color the day I water, only to return to shriveled in the next few days. Any recommendations to help her adjust to the new type of medium? Should I go back to sphag? A different medium? I've got some marbles I'm thinking of adding to the bottom of her new pot to increase drainage. I'm going to make a humidity tray out of said marbles, as well.

I'm also worried because fuzzy white suspected fungus (pictured below) has shown up on some of her roots that stick out of the top of the potting medium (pot is too short) so I know I need to repot her, but I'm afraid of traumatizing her further :-/ I've read that I can treat the fuzzy mold with hydrogen peroxide which I will do when I repot her into her new pot within the next 2 days. Could I also add vinegar to the new medium, whatever it is, to increase the acidity? From microbiology class, high acidity inhibits fungus growth. Any suggestions on how to combat the fungus? I've heard of sphag and bag, but I'm afraid more mold will form :-S Other suggestions for nursing her back to health?

I'd pull her out of her bark-soil medium to take pictures of her roots, but I don't want to do that right now until I'm going to report her to minimize the stress if at all possible. So I'll post pictures once I figure out what medium she'll be going into. Any other pictures/info you'd like to see/know?

Any advice and/or criticism appreciated! She's my first and only orchid and I want to protect her. Thank you in advance, especially for slogging through this post! Please help