Bulbo roots with black spots and yellow dust on Scaphosephalum

[Eritrean]

Hello, this is my first post on the forums. Sorry if I've missed anything, but almost all the reference images for orchid diseases are on Phal orchids and I only have pleurothallids. I'm also terrible at diagnosing stuff in the first place.

I grow all of my plants in a large terrarium with ~80-90% humidity and 70 degrees fahrenheit. I mist heavily once per day and usually have a small fan on for an hour or two.

My Bulbophyllum ovalifolium dropped many of its leaves previously when water was left sitting on it for too long, and although two of the cuttings are doing okay, one of them has struggled a lot. It has brown regions on its roots, as the others do too, but it also has black spots popping up and the oldest pseudobulbs are highly pale and slightly shriveled.

I also have a Scaphosepalum rapax from ecuagenera with a yellow "crust" of dust on its leaves that won't come off with water, but can be removed if I scrape it off with my fingernails. Should I be worried about this? It's also on my Biophytum zenkeri from the same source, of which I've attached a picture of.

Also, on my Dinema polybulbon and Bulbophyllum alkmaarense, they've been growing okay, but the growing points have shown some growth but then turned brown. Did I leave water sitting on them for too long? They were both mounted pretty high up in my tank, so I thought they would dry out quickly enough.

Lastly, my Restrepia mendozae has started showing brown splotches underneath a leaf. Is this a bacterial infection? How would I treat it? It's also present on some of my plants, but far smaller. It also has a somewhat young leaf that has had white spots on it for weeks. Should I be concerned?

1st picture: Two healthy cuttings of B. ovalifolium
2nd picture: Root-side of the two above cuttings
3rd picture: Unhealthy cutting of B. ovalifolium
4th picture: Leaf of Biophytum showing the yellow crust (Note: there's no dirt on the leaf. It would be a solid green if not for the crust)
5th picture: Restrepia underside
6th picture: Young Restrepia leaf with white spots


Thank you so much for your help.

[aliceinwl]

I have no idea what’s going on with your plants :-( But, if no one chimes in it may be worth posting to the subforum on terrarium growing in case the tank set up plays a part in what’s going on.