We just noticed that our CT has lighter colored spots behind his head. It kinda looks like he would almost be fuzzy to touch. We do 10-20% water changes twice a week. Last night the tank did get pretty cool. It was down to 72 F when we got up. (I hate the heaters we have). He isn't acting funny, he is as active as always. He does seem to be a bit puffy, we just did a water change last night. Our VT betta and cichlids are doing fine, so I'm thinking its not the water. I am trying to upload a photo of him. Any help would be greatly appreciated, we are still somewhat new at all this.