I have a one year old Pit mix that I adopted from a rescue last year. I started transitioning her from Pro Plan sport to Wellness Core. She's been doing fine with the transitioning so far. However, I got a message from my mom saying that my pup has had diarrhea twice. Does it take longer than a week to make a transition? I felt like switching her to grain free would be best as I've noticed her itching more. Any advice would be great.