I've noticed that in both Toby and Delilah, and misting their tanks for a few days seemed to do the trick. The climate here is very cool and dry, so I guess the humidity wasn't quite high enough... it usually lingers around 48-49%, so maybe 50% isn't doing it for your BP. Here's a picture where you can see a small dent in Delilah's eye, before I started misting (she's now back to normal).