Instinct Check: too much humidity?

[reptilegrrl]

Hey y'all. I have an oncidium (fka wilsonara) Firecat 'King Snake' that a friend gave to me as a rescue. It was in very bad shape when I got it, no live roots, lots of rot and mildew in the pot, some bacterial infections on some leaves. I have it potted in a 3-inch pot with Monto Clay only. It has one small new growth chugging away. AFAIK it has only one small, short root on the new growth.

I had it in medium light, but I moved it into lower, indirect light because the older PBs were shrinking hard, and with only one root I was concerned it couldn't keep up with the moisture needed by photosynthesis. It seems to grow in fits and starts. I thought maybe it needed more humidity, so I set the pot in a large vase with leca and water in the bottom. Not touching the water, uncovered, etc. It's been in there about a week and yesterday, the remaining "sheath leaves", the first outer leaves, turned black. The tip was dryish but the base was wet. I've pulled off as much of the black as I can and sprayed it with Listerine.

Am I correct in thinking that this means it was too humid inside the vase? I'm wondering if I should put it into the vase but move it into a dryer, high-light position, or keep it out of the vase in this low light place.