my condolences on your loss, but realistically, you cannot go from feeding a nutritionally poor, bland food like Science Diet to a rich, nutritionally superior food like Wellness Core without some consequences. Science Diet is a grain based food with very little meat in it. Wellness CORE is a grain-free food that contains more meat than carbohydrates. It's like comparing apples to bicycles... the two foods are so vastly different as to be light years apart. If your dogs' sickness and death WAS caused by the food itself (and I would doubt it, and suspect some hidden medical factor dealing with, perhaps digestive enzyme imbalance), you should contact the Old Mother Hubbard Company, manufacturer of Wellness foods, and issue a complaint with any product information included.