Our 13 week old puppy Zorro has suddenly lost his appetite. He had his usual 1.5 cups in the AM yesterday and since then has not eaten much. Has been drinking water (although a little off there too). Since this morning his energy level is low too. I intend to watch him till end of day today and take him to the vet tomorrow if it doesn't improve. Has anyone experienced this with their puppy/dog ? What are the likely cause ? Inputs are greatly appreciated.