Sick Acropora?

[Brett H whitt]

Looks like something is damaging my Acro. It’s been in my tank for about 4 months with no issues. All my other corals look fine so far. Anyone have an idea what this is. The pictures do not do the coral justice, it’s a very nice piece.

 

[bios]

The black stuff in the first pic ,
You see it moving on your acro?