I just got a new doe that I plan to breed. she is alone in her cage at the moment as I plan to keep some of her daughters with her and don't want an over run cage when I do breed her. I think the isolation is getting to her, even though I socialize her much more then any of my other mice. She won't run on her wheel and never comes out of her nest/box area. Everything physically, as far as i can tell, is ok. I won't be breeding her until late May because she is still quite small and I'm guessing only 4 to 5 weeks old.