usually poor water quality or no water movement. Check the pumps and water quality for ammonia nitrite, nitrate & PH. They will also look a bit wierd first thing in the morning but should look normal after an hour or so of the lights being on.
Thanks guys. Mysteriously, he is all better now. They did reflate and he looks fine. I don't know what happened. Maybe a crab gave him a poke or two.
No, I am not doing the blackout anymore. I had put the halides back on last night and did notice that the dino's were already growing back that quickly. I also set up my phosphate reactor and added carbon the water last night. So, lets see if that does it.