Ditto. I had a similar experience with two yearlings softshells from the same clutch. both the same size, but one seriously injured the other in a feeding frenzy. Its fine now, but with disfiguring scars in the head and neck that prevent it from extending its neck completely. I now keep all of my turtles separate, even paints and sliders. Better safe than sorry.
Ed Stone, WI herp. society