I think I would quickly go back to what was working. In the meantime closely compare the ingredient list between the two foods and try to nail down what may be so different and objectionable…maybe a different fat source that she is having trouble digesting? I used to spend a lot of time trying to make something work…or thinking that it eventually would,but I rarely do that anymore…and with a dog that is actively being shown there is too much too loose to continue on with something that is working well all around.
