I have this one group of Zoanthids that closed up suddenly after i did a water change 3 days ago. At first i thought that it closed because a bristle worm was crawling around at the base and irritating it, but today i took the group out of the water and the worm was gone , but the Zoa's are still closed. Only 1 polyp is opened and it seems to be a bit away from the rest. I noticed that sometimes the other polyps will open up partially then close again. My other groups of Zoa are doing good, opened and colorful. So anyone have any idea whats up with that one group? My water parameters are good 0 ammonia, 0 nitrite, less then 20 nitrate, salinity, and gravity are good as well. All my other corals are doing great, just that one group of Zoa's.