My first thought is that it could be food allergies. When I first adopted my RB Storm, he also lost the fur on his ears. The vet at first thought that he might have ringworm but the test was negative. I was feeding him canned & dry food that had a lot of fish in it. It turned out that he was allergic to fish. Once I stopped feeding him food that contained a lot of fish in it, his fur grew back. She could possibly even be allergic to chicken even if she wasn't before. Hopefully you'll be able to find out what's causing this. Good luck.