Open Brain Coral Looks Weird

[Pier Pressure]

Good morning.

I have a green and red open brain coral that has been thriving in my tank for over a year now. This thing has tripled in size and is a very good eater that I direct feed a couple of times per week.

Now I am noticing a small part of it looks burned or something. The skeleton part is showing through on about a half an inch of its outer rim. Should I cut this piece away or medicate or something?

Fish and other corals are doing well, water is right where it should be - so we are baffled. I think it might have gotten stung by a tube anemone that we have since removed from the tank. Once that thing started moving it took out about half my ricordias as well.

Please help me save my brain! Sorry I do not have any pictures.