My puppy (11 weeks old) is eating Canidae. We switched her over from Purina (which she was getting at the rescue) between 8 and 9 weeks. I was hoping that would resolve her itching issue, but it hasn't. What are the odds that she is allergic to something in *both* the Purina and Canidae? Or do you think I should be thinking this is something other than a food allergy?