Nice tank. Is that a tongue coral on the bottom left?
Yes. It's a funny coral. All of the tentacles will retract to the point that I think the coral is dying and then it grows a little bigger and the tentacles come back in force. It's a pretty neat piece.
NICE TANK!
Is that second pic a spiny cup? I love the color!
That might be the reason why your crocea aren't doing well. Tongue corals are very aggressive.