Hi Leslie,
I recently had the same problem with my girls after feeding them food without probiotics for a few months. I do not think Science Diet puppy has probiotics in it and your puppy probably has not developed enough gut bacteria yet to handle a transition. I know a lot of people say the probiotics in kibble are useless, but I never had a problem doing a food transition when my girls were eating a kibble that had probiotics.
I would suggest adding a good dog probiotic with multiple strains of bacteria and a prebiotic in it, or if you use one without prebiotics, add kefir, yogurt, or goat’s milk in also.
