What bedding do you use?
Is she handled by children at all?
Is she new to you?
This could be skin mites, nutritonal problems or be a skin fungus called ringworm.
You can read about skin mites and their treatment here
http://www.guinealynx.info/parasites.html
and they are often not visible to the eye.
You can read about ringworm fungus here
http://www.guinealynx.info/fungus.html
Nutrition here
http://www.guinealynx.info/nutrition.html
and more on skin issues here
http://www.guinealynx.info/hairloss.html
I cannot see the ingredients in the Critter Care bedding but if it has pine or cedar in it then those can be an issue. Many small animals react to the volatile oils in the pine or cedar shavings with a skin issue.
I'd plan on seeing a vet with your pet if the bedding is not the issue.
Hope this helps you!
If its skin mites treatment with ivermectin usually is a quick cure or possibly you could use Revolution in the right dose.
If its fungal infection its usually a topical treatment.
Both would require vet care because the meds are prescription.
You can read about mite treatment here
http://www.guinealynx.info/mites.html
Pet Health Care, Rescue,Train,Breed
30+yrs pet vet care & nursing, rescue, behavior & training, responsible breeding, small animal care