I'll give my thoughts for whatever it's worth (I have only one small Pleurothallis species). I have no way of knowing what the problem is, but my first thought after seeing the limp leaves was that the root system is the problem, maybe from over watering or media breakdown. On the other hand, shriveling and purple in the leaves can mean too much sun. There are a lot of Pleurothallis species out there but I think generally they are considered low light species. I would suggest looking at the quality of the roots and the media (repotting and pruning back if necessary) and putting the plant in a low light situation.

wuness

I'm guessing - too much sun? Don't know why the leaves would be limp either unless the roots are bad. Follow wuness's advice.

Jane