sick zoanthids

All my zoas are doing good but this one frag of Rastas and I don’t know what’s making it stay closed originally was open for like the first week about and then slowly one by a be close out of the four polyps.

Help!! I have had my zoas for about 2 weeks now. For the first week they were doing great, opened right away, polyps fully open and great color. One day they just suddenly didn’t open one morning and have not opened for a week and a half now. I am really worried because I have searched...