zoa shrinking

Ok so I've got several zoa frags with heads getting super, super small. they aren't melting or dying but the heads are maybe 1/2 to 1/3 the size they were months ago. I have recently had a cyan outbreak but they were shrinking in size before this. Any ideas what the problem could be? Biocube...

I have several zoa frags whose heads are getting smaller. They aren’t melting and they’re still reproducing fine they’re just smaller. If they’re ok I don’t see it being an issue I like my polyps to be relatively the same size anyway. The zoa in question are my vamps in drag, purple monsters...