People have told me that some softies (like xenia) will die off and come back. Will zoas do this? I've lost two clusters (out of 5) of zoas in the last few months. I thought it was water conditions, but my specs match what people post as healthy. I thought it was my lights (4x65w PC), but my shrooms, rics, leathers, torches and other zoas are doing fine. These zoas stopped opening and eventually turned a very dark color and seemed to disintigrate. Are they gone forever? Should I be shopping for new frags? Is there any common tank issue that I don't know about that may have killed them?