Hmm could be an allergie. I hear staff infections can have a particular smell. Anal glands can release fluid sometimes. Its a fishy smell. I'd bring her into the vets for a chek up. I would not let them make you put your dog on some Hils science diet bull either. Make sure your dogs food has no corn or wheat in it. Many dogs are allergic to those items.
Whoever said you can't buy happiness, must have never owned a dog!!!!!!!!!!!