Open Question: Ferret losing hair on it’s tail?

My roommate who is from the family through the months of ferret no longer let her come back. When we get her, and she is quite thin, and hair loss on her tail. We have never before ferrett, but each of us to say, hairloss, as normal, and sometimes occur. She's good food, because we got her, and has been restored to a healthy weight or weight. (I do not know what other people's work, so that she lost a lot, when we let her). She looks completely normal, but the hair on her tail never grow back. The season is changing, I'm just under her door, and hope to have more hair did not look up to her tail, about what … anything that might cause such a way? We should be concerned about this?