I just read a post about how a lot of you out there really are satisfied to the way your Chi's have responded to Royal Canin. I'm very interested in purchasing a bag for Seiah. However, I just went on Petsmart's website and saw one specifically for Chihuahuas. But in the desciption it read for Chi's over 8 months old. What have you all been feeding your Chi's. Also should I slowly change it out or just use RC? Or if he responds well then is it okay to just stop feeding him his other brand?