Schoenorchis seidenfadenii

[Leafmite]

I do not grow this one, either. I grow Schoenorchis scolopendria and fragrans. You might want to give Andy's Orchids a call and describe the symptoms and ask his advice. He is truly an expert on orchids.

Black roots are often a sign of too much fertilizer, fertilizer build-up, or some other chemical burning them. This can also make leaves fall off.
I killed my first fragrans due to calcium deficiency, along with many of my Cattleyas. So, they seem to need a constant source of calcium (who knew?). They are also, like most Vanda-types, prone to crown rot so it is important to water in the mornings. I cut the tops off of plastic water bottles and set them inside, stick and all, to help with humidity as I am growing under lights and everything dries quickly. I put a little water in the bottom of the bottle and the stick wicks it up to the roots.