Kirkland Puppy Food

My puppy was eating the cheapest Petsmart puppy food at 7 weeks old. I switched her to the Costco Kirkland's puppy food (gradually). She is now 11 months old and she would get loose stools every couple of months. Now it is twice a week, and she has no other symptoms of illness. I'm thinking it has to be the food. Anyone know what ingredient it is in the Costco food that I should look to avoid in whatever I try to switch her too? Should I just start switching her to an adult food? She's an 11 month old yellow lab.

Pros: She loves it! And the ingredients sound good

Cons: She had chronic diarrhea on it :(

I fed this to a number of foster puppies last summer. All seemed to do well on. It is, perhaps, not the highest quality food available but it's at least as good as Science Diet, Iams, etc.

Pros: Fairly good ingredients, good price

Cons: Not the absolute best