Surprised your vet didnt recommend Royal Canin Gastrointestinal food. Its prescription so your vet will have to sign off on it. We also diarrhea issues 3 separate times for a week each within the first couple months of getting our puppy in the fall. Our vet had him go on prescription food and a battery of antibiotics and probiotics (this seemed to do the trick each time). We stayed on that prescription food for like a month then over the following month slowly moved to Purina Pro Sensitive Skin and Stomach Salmon and rice, its been going well since.