need help!

[makana]

I'll try and get a pic tomorrow. I just finished the water change and the coral is all closed up. The tissue on the bad side appears to be receding and the skeleton is exposed. I checked the new water and calcium was only 400 and alk was 8.96dkh.

There is a hermit crab, cleaner shrimp, clown fish, and chromie. I havn't seen any of them bother it and none of them are new, but I guess it could happen.