So, I don't know if I jinxed myself or what but I noticed my calcium reactor was not dripping into my tank. So, I unplugged the inlet and purged a good size stream into the sump, not thinking, and immediately my xenia, gsp, and bta shriveled up and look horrible. I shut off the reactor and dripped kalk all night and got the pH back up to where I am used to running. They are all now recovering but it is taking an amazing amount of time, a couple days and they still aren't back to normal. Is it possible you are getting some sort of spike that could be irritating them? Like I said my parameters where all back to normal fairly quickly, and the weird thing is my SPS seemed to not be affected in the least. I don't understand it, but thought it might be helpful to you when trying to help your RBTA.
-chris