Because the hair loss seems to be spreading, Gina, we would recommend a return trip to the veterinarian to have your puppy reevaluated. Demodectic mange—caused by a mite transferred from mother to pup—can be challenging to diagnose with one skin scraping, so your veterinarian may want to repeat the process. However, there are other possible causes for your puppy's hair loss, including nutritional imbalances, fungal infection, allergies or other external parasites like fleas. Your veterinarian can perform further diagnostic tests to try to determine the cause of your puppy's hair loss and work with you toward a solution. If your veterinarian is not successful in determining the cause, you may want to ask for a referral to a veterinary dermatologist.
There are also several things you can do to help keep your puppy’s skin and coat healthy. Feeding her a high-quality, nutritionally complete puppy food, brushing and bathing her regularly and keeping up with veterinary care and parasite control will all help promote her healthy coat.