I'm also having a problem with my bully not eating like he used to. My Jax is 5 months old and has been on Blue Buffalo lamb and oatmeal since we got him before Christmas when he was 2 months old. He has always scarfed down his meals, but in the last week he barely eats his bowl of food. At first I thought that maybe he was getting sick or something, but he would go and try to eat our other dog's food (yorkies who eat Iams) or the cat food. So he is definitely not sick and is hungry, but it sounds like he may be sick of the flavor of his food.
He has also been having tiny bits of chicken and a tablespoon of either cottage cheese or yogurt mixed into his food since he was three months. He has always loved it. Now I am not sure what to do.