Posted: Mon Aug 10, 2009 7:05 pm
He was OK when you first got him? How long have you had him?
What are the temps of the water and basking area? Does the room he's in have AC? If so, could he have gotten a draft?
Don't put him in the water "upside down"---he could drown.
I'd separate him and give him his own set-up; what he's got is likely contagious, and that many turtles in a 10-gallon tank is way too much anyway. Keep him warm, water temp 80-82F and the basking area around 90F and keep him out of any cool drafts or breezes. Don't make the water very deep (but a little deeper than the length of his shell).
Try to get him to eat---hold a bit of something smelly in front of his nose in the water and see if he responds at all. it would be good to look for a herp vet while you're doing this in case the added warmth doesn't help and he still refuses to eat.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-