Check the Zoas for pest nudi's. If just one gets on the colony the whole bunch will close up. They are hard to see but if you look close you will see them. You may also see small white rings. Those are eggs. I had a few colonies that would open great for awhile and then close for weeks at a time. I found the nudi's munching on them. Killed the nudi's and the Zoas and Paly's opened up the next day.