I have 2 clawed frogs that were purchased at the same time. One albino, one wild type. When I got them they were pretty much the same size. Both appear to be females, but the wild type frog is almost twice the size of the albino now. Neither is done growing yet either. I am sure part of the reason is that the albino had an injury and has been regrowing her left hand. As a result she eats less and of course more of her energy is devoted to healing/regenerating.
At what point should they be seperated to prevent cannibalization? I had this type of frog years ago and know first hand that smaller individuals can "disappear" without warning, well fed or not. I definately want to keep them together in the long run. I think seperate they can even up in size as I can regulate who gets what as far as food.