Sunken leaf spots on masdie
 

What is this? Bacterial brown spot, something fungal? Just wondering if I need to do or buy something special to treat it.

Day 1:
https://i.imgur.com/qHU9bmG.jpg

Day 2, back of leaf:
https://i.imgur.com/RFqgoUi.jpg

Day 2, front:
https://i.imgur.com/3QI62Zc.jpg

This Masdevallia ignea ‘Valentine’ x discoidea ‘Anne’ keeps losing leaves, it’s down to 2 (but has at least 4 new ones developing). It gets these sunken patches, they start on the back, spread to the front and then turn brown. I thought it might be crowding or water sitting on the leaves, so now it’s in a spot where it doesn’t touch anything and water evaporates quickly, but I just lost another leaf. I cut them off with sterile scissors (maybe not sterile enough? I hold them over flame, but I could buy single-use blades), and when I moved it I sprayed the leaves down with Hydrogen peroxide - maybe that just ended up spreading it?

My temps hit 80 but have a good daily drop into the upper 60s, but the seller was not growing it cool. It should get warmth tolerance from the discoidea and it doesn’t have any of the black speckling that you often see indicating heat stress in Masdies. It was very healthy and in bloom when it arrived, great root system. I checked the roots but they were so healthy that I didn’t repot, just left it in the bark mix it came in.

Cercospora maybe? The pictures don't look like it but it says it begins on the back of the leaf. Would Physan20 work for this?

What is the humidity?

Until a week ago it was in an Exo Terra orchid terrarium, where humidity ranges from about 60% to 85%. It has ventilation strips (too much ventilation at the moment, actually) and a fan that runs twice a day for half an hour - if I run it any longer, it drops the humidity too low. I need to fix the ventilation in that tank, but haven't gotten around to it. Essentially, sphagnum on mounts dries within 24 hours, but water on leaves sits around for hours - I think I can fix this by running the fan constantly but having less ventilation.

Then I moved it to my jewel orchid glass bubble bowl which isn't as crowded. Now it's 80-85% when it's covered all night and most of the day, but every day I remove the cover for a few hours, water the plants if necessary, let them dry, and then replace the cover. At that point it drops to 55-60%.

I've been avoiding getting water on its leaves altogether since moving it, and any droplets of water on anything have dried before I replace the lid on the glass bubble. Nothing is soggy in the bubble despite the high humidity, there's no condensation on the glass, I would say the substrate is just "lightly moist" and the Begonias and jewels I have in there are growing well with no bacterial or fungal issues on their leaves.

Anyone?

Update: it got down to 1 leaf but Physan + removal of the leaves with spots seems to have handled it, it’s back up to 4 healthy leaves now.