ACRIFLAVINE 15-20 minute soak every 2 days. This is a fungal issue, pristine, warm water at a high PH 8.0-8.5, marine salt and bring it up to pretty much brackish conditions .004-.005. These turtles get brought in at a small size in mass amounts and the conditions they get shipped over in are just terrible, but when a turtle costs $25 and you can resell them at a much much higher price, people won't care. If you feel like that's not working after about 2 weeks or it gets worse, you can attempt to use betadine, let it dry on the area before putting the turtle back in the tank. Personally, if it got worse I'd take it to a vet. But, if you do all of the above, you'll see good improvement quickly, just hope the fungal infection didn't go too deep.