If you're still feeding your dog, Royal Canin, you should change it. It really is a poor quality dog food. Just because there's a picture of a GSD on the bag doesn't make it a good food. I think Carmen was completely accurate with her original diagnosis. Besides being wary of vets, you shouldn't completely trust pet food stores. I think they all have corporate deals with the dog food companies so they have to really market (sell) these dog foods, even subpar ones.
Ask on the forum. I believe in less or no grains and no corn. If there's any corn (including corn gluten), pass on that food and consider another one.
Raw is best, imho, but the next best alternative is a kibble with decent ingredients.