I agree with the other post about the need to transition slowly over a period of a week. Old to New ratios for several days on each: 75/25; 50/50; 25/75
Another thought: the Innova Adult has more calories (504 kcal/cup) than either the Innova Puppy (454 kcal/cup) or Innova Large Breed Puppy (367 kcal/cup).
If you haven't reduced the amount of adult formula you feed, your dog is getting more calories than he is used to. Even eating more than he is used to by 1/4 cup could cause loose stools.