first things first is it a m and f ferret you have as my man was a breeder and keeper of ferrets . if yes its coming in 2 breeding season and that could be the reason for this , and the male ferret always losses some pounds at this time , if you want y could put up some pics and tell me a bit more and ill pick his brains, as he was great with ferrets and always new what was going on , its could be worth a try ,, money isent always at hand when y need it so dont feel sad about it ,, will be ok