It could be the Purina puppy food. Most of the members on here will recommend that you feed you puppy a 4 star or higher grain free puppy food. I know that when Toby was on purina it made him have the runs non stop. I changed his food and he has done great since then. Good luck!
Mother to Toby (Male, Brindle, Floppy, Docked) Born on 11-8-2011