i have an elegance coral which i placed in my tank several weeks ago, it seemed to be doing fine, brightly colored, etc. a few days ago it "sucked" itself into its skeleton, and hasnt come out since. it is so deep into the shell that it appears it is not there. also today it had a bunch of noticable slime all around it. i have repeatedly checked my water conditions and everything is fine. all other corals seem to be doing well. has anyone seen anything like this before? what could cause it? i havent lost anything in my tank yet and dont want to, any ideas would be great help