i have 2 mollies, 1 mollie is fine, the other one [orange] is lying on its belly tipping sideways and back up then sideways again and back up!?! its not moving, all the other fish look fine, cept for that one!
Sounds like swim bladder disease. Seperate them if you can and treat with salt until you get some swim bladder meds. Don't think it will last the night though.