I don't know what happened. Had to scoop her out this morning and flush her I've only had her a week. Last night she was at the bottom of the tank, upside down and still breathing, but she kept snapping out of it and would swim again. Thought maybe she was playing dead, for that afternoon I had literally just added 3 new mollys, though maybe she was scared....? Could it have been the water from the pet store? Or was she scared to death? My water checks out perfect. All my other fish look healthy and happy. It's a mystery.