I am so sorry about your mouse...the poor little guy! Well, the good thing is that he seems happier in his own habitat now that he is not getting picked on by the other mice, so at least that has to help him get some relief from the stress of getting picked on. (what is his name by the way?) but if his fur is still falling out, even though he is now separated from being picked on, that is one I am not sure about. Hopefully you will get some comments from people on the forum who know more about mice than I do. My own experience is only with gerbils and rats. In the meantime, do you have a good small animal vet you can call and ask about the fur falling out? My local small animal/exotic vet's office was always a great source of help with my phone calls when I had a concern.