Root problems with Pleurothallids

[shakkai]

Yes, my guess is the humidity. Most Pleuros like to be on the damp side, and with it being mounted, I'm betting it dries out to quickly. If humidity isn't high, the plant will be losing quite a lot of water through its leaves and literally sucking the roots dry.

I use tap water when I run out of rain water, and so far there has no adverse effects. Though I have heard from many that there are some Pleuros that are extremely sensitive to water quality.

The first thing that I would address, though, is the humidity around the plants.