well this post may be late but ill add it anyhoo lol. i have a trio of RES and 2 of them developed red patchs on there feet and upper hind legs. i racked my brains trying to figure it out untill one day i heard a ruckus from the tank. one of the Turtles was getting aggresive and would grab the others by the hind legs and pull. it got so bad the other 2 would only swim around with 3 legs exposed. pulling in the hind leg closest to the offender. if you notice this it may be your problem. just watch carefully and listen, thay normally only did it when i wasnt in the room for a long duration. once thay get comfortable in the fact thay are alone. i hope this is all thats wrong.
