Spring coral losses

[KPG007]

I've been having a strange case of losing Zoas. Sps - all fine, LPS - All fine (not true, I had two new chalice frags wither and die, but they were new, so it may just be a coincidence), only Zoas. I have two tanks, and all the death has started on one half of one tank (the other half, all the Zoas are fine)! Strange thing is two Zoa frags have grown like crazy in that area. Moving failing pieces to the other tank has helped with some, but not others. I'm thinking a flow or algae issue.