Mine have white spot too. But after a few days, they disappeared. It seems that those zoas with white spot will not open fully.
I think might the water change solving the problem.
Saw that the mantle was loose. Also, there's worm attacking within the mantle. However, the siphon was moving but not sure if it's the water current.
Heard that if they died within tank, will release toxic, so quickly remove it.
Need help. My clam had fallen off the rock and leaving behind a lump of fresh. Is it normal? Should I remove the lump discharge? Is the clam dying?
So far, still responding to light.
I've moved it to another location.