Wow now that looks painful! Pretty bta, I dunno if the white base means "bleaching" or not. The tentacles seem to have plenty color.
The only thing I can think would do this is a filter or pump output flowing directly on it. BTA's don't need a lot of heavy water flow, so if you happen to be hammering it with water, move the water outflow (try to bounce it off the glass to created a turbulent movement instead of a straight laminar flow).
One note, BTA's are one anemone that needs to be fed, either via a huge refugium or preferably some whole crustacean. Ron Shimek's book on anemones recommends whole small shrimp, like frozen mysis.