After more than two years of thriving, my hammer corals for the past couple days are not opening up full. I started with one three branch specimen, it grew to six branches and I broke a piece off giving me two three head specimens. These have each grown to six or seven heads and were looking just great until several days ago and they just stopped opening when the lights came on. Have checked all water parameters and they are all the same as they have been for a couple years, all other corals look just fine. Anyone have any ideas?