Get canned pure pumpkin and start adding a spoonful to their food at each meal when you start the change. Give digestive enzymes and probiotics, human ones from the health food store o Swanson’s online ae just fine.
The issue is that after eating the same food for a while the dog’s body adjusts to that specific food. It produces the enzymes needed for that food and the probiotics that are not supported by that food die off. The new food needs different levels of different enzymes and a different mix of probiotics to help digest it. After your dog has been completely on the new food for a couple weeks, you can start trying to decrease the added stuff, but I give enzymes with every kibble meal and probiotics a couple times a week for life.
