Skin lesion on foot

Question
Recently one of my red eared turtles has developed an open skin lesion on her hind leg(bloody ooze) and have treated her with a sulfa dip as well as betadine solution directly on the lesion.  What caused this and am I treating her correctly.  A male bites the effected leg when he gets by her, so I have isolated her until it heals better. She also has been basking constantly, no appetite that I can detect.   Help Please.. Thank you in advance, Barbara

Answer
"Clean the injured area with clean water. Disinfect the area with iodine or betadine. Treat with Silvadene (Silver Sulfadiazine), Neosporin or triple action antibiotic. Let turtle be dry for about an hour after treatment. Place in separate tank with clean water. You can add StressCoat for fish as it assists in the healing process. Treat this way daily for about 2 weeks or so." (http://www.austinsturtlepage.com/Care/medinjuries.htm#Bites,%20Cuts,%20Burns%20a...)

You will also need to re-evalute the set-up using guidelines form places like http://www.redearslider.com or http://www.austinsturtlepage.com

Your tank may be too small, and the water temps too cool or something.