It’s either water or lighting, and I would think more of these type of issues are related to water. It makes a lot of sense because it’s water intake that makes zoas/palys get big.
I just fragged a large colony up and I was amazed at how much water the colony expelled once I started cutting it and breaking it up. I had some stalks that were 1.5” long that shriveled up. Once they got back into the tank for a few hours they sucked up water and got long and full again.
Start spot feeding them, I’ve had problems with zoas in my tank and they would shrink up and disappear I tried moving them different light futon 2 dips addition Bauer dips and once I started spot feeding them they recovered
ph change or salinity change see this happen from time to time... expecially ph change i grow utter chaos on top brightest par and do not see this situation occur like yours...
I've never had much success with Utter Chaos, and always liked them. I had a bit of a disaster a while back when my RO unit started messing up. My digital meters said I was at 0 ppm....but they were wrong. As it turns out, my tap water was about 7-8dkh before adding salt mix...which sent it upwards of 14dkh. I didn't notice it until some corals started dying. At the same time, my UC palys were doing better than ever, doubling in size and numbers. I now suspect they really like high alkalinity.