I would try boiled plain chicken and white rice for a day or so. Then I would change his dog food to something that has less fillers in it like Solid Gold Wee bits, California Natural, Verus, Candidae. If you have a small pet store anywhere near (not Petco or Petsmart) go there and I am sure they will have those. If not I would google the food and order online. It's well worth it for the health of your furbaby
Also I mix Georgie's dry food with some plain non-fat yogurt maybe 1/4 tsp. and he loves it. Hope your baby feels better please keep us posted.