We are switching Blue's food. We don't feel that the BilJac we are feeding is doing the job, and we found a food with High Protein for active dogs, that Blue loves. My question is how long should it take to wean him off the BilJac? Right now he gets 2/3 cup of Dry BilJac, 1/3 cup Nutro Natural Choice, and 1 cup of the refrigerated BilJac. I know it's going to take time, but when should I increase the Nutro, and in what increments? I don't want to do it too fast and upset his digestive system...