crab in eye of chalice

[iceman86]

I've had this chalice for about 3 months and its slowly been bleaching away to the point where half of it is white. I've tried everythibg with this coral from moving up on the tank cuz where it came from it had strong lighting and then to a shaded area and nothing changed. Last night I decided to creep up on the tank 2 hours later after lights out. I found a small crab inside the eye of the chalice. All I could really see is his claws sticking out and moving around. Could this be the reason its bleaching? And how do I get rid of the crab?

I also just installed new led lighting and the other day I came home and my mushroom coral was dead and one of my Monti caps was getting white spots on top. Could this all come from the same problem or is my light too strong. I already turned it down.

Thanks