It might be the food try changing her back and see if she better, have you bath her in anything different then you usually do. you might try a mediciated shampoo or a oatmeal base shampoo. I am now using micro-tek shampoo it has work well for me heres a link
Micro-Tek Medicated Shampoo (Pet Supplies - Grooming (Pet) - Shampoos Conditioners - Medicated)
I started using this after my favorite shampoo was pull off the market.