plate coral being eaten?

[Snappy]

This was like this 2 days ago, yesterday morning I noticed it was down to the skeleton on about 1/5 of the piece on one side, now it is at about 1/4 gone. It hasn't been touching other corals and there has been no changes in the tank other than adding a frag of devils hand with is located about 3 feet away from the plate. Is it starting to die or has something discovered a new delicacy for snackin'. Anyone have any idea what eats these?