Yesterday I picked up a birdsnest frag. I just noticed a few tiny patches of tissue loss. Polyps are extended though it still looks a little brown. Trying to up load a photo
Is it possible that you didn't notice the bare patches were there before you bought it? If you're certain it happened in your tank, there are a lot of plausible scenarios, stress from acclimation, poor water quality, poor water chemistry...
I believe it was like this at the store. I checked at at the store so did an employee, but since it is so small we probably just missed it. I noticed it shortly after I put it in. The tissue loss hasn't gotten worse, that I am certain of. Yes there was a nitrate and posphate issue. Something went wrong with my skimmer and is now fixed so the small cyano/algae problem is dying off. Phosphate is still slightly above zero, mag is a little low at 1200, calcium is 420. Nitrate is zero as well as nitrite and ammonia.