That's too bad about the flesh peeling away. It is a hardy coral that likes high flow and high light. Something is not right.
I think I know what's not right

I got it from friend of mine, which usually buy tanks brake down (when the people can't afford the hobby or need fast cash, or just are tired from it, hebuy most of them tanks and later on resale the stock

), so he isn't good in one think, to acclimate the corals properly, and also to separate them. Now in his 3 coral tray tanks, hehave over 70 BTA which are stinging everything in the tanks, not sure this one it's been stunt or just isn't acclimated properly. Sometimes he just move the corals between the 3 tanks, to rearrange them, and again isn't acclimating them at all even when have 3-5 deg C temp. difference.
Will see, I lower the flow on it now, and put shade over it. Also today I try to make it puff with food

target feeding with food for filter feeders and I add also reefroids.
I just check it now and it look a bit better, start to fill the space around it (look like it's extending, but no way to see polyps yet.
Not sure what food to suggest to make it come out

(just not enough info about)