Hello Mia,
The pictures were great, you have some adorable ferrets!!
 
I'm not a vet, but to me it sounds like it could be adrenal disease.  I'm
sorry to say that, but it sounds a lot like what happened to my Chong.
She never had a swollen vulva, but had the hair loss and the increased
nipping episodes.  She ended up having surgery and is doing great now.
You should get to a ferret experienced vet as soon as possible.  Not to
scare you but, if you wait too long it's possible that they can get
anemia, which can be quite serious.
 
Hope all will be well soon
suzi
[Posted in FML issue 4239]