I think my dog may be allergic to her food?

Could be allergic reactions. Dogs can have allergies to things besides food. The only way to know for sure what the dog is allergic to is to have testing done. If you want to try changing her food, look for one with no grains. Ingredients are the issue more than the brand, but Kirkland isn't going to be the best quality. I'd switch to a higher end brand. Might not cost any more because with the better foods you can often feed much less. Corn, wheat, and all meat are often the culprits. I use a fish and potato based dry food for my allergic dog. And if your budget can stand it, many people find that GSDs do very well on a raw meat diet. If you change food, remember that you can't expect to see any real change in the symptoms for 2 weeks and it could be longer before the effects of the new food take hold.