It’s diet is likely not agreeing. Try a couple of different dog foods. My Boxer was bad with the runs and potato duck did the trick. Chicken is the likely issue.
@Soramarie Most dog food has chicken even if the package says something else. I had to go to a limited ingredient food like Blue Buffalo or Natural Balance. Blue quit making my duck but Natural Balance worked well.
@Livingwell Diamond is like one of the tops. I’m thinking of switching to for health which is like tractor supplies blue Buffalo. And trying to switch meats again