I have two sibling Sih-Poos who are 4 months old. They began with vomitting yesterday along with diarrhea and today they continued with diarrhea alone without the vomitting . I have been feeding them Royal Canine #33 for puppies. I have been giving them 1 tbs. of Wellness canned puppy food with their dinner or 1 tbs. of cooked chicken. Would this do it or would they have some type of parasite or virus? Life at home is typical so there is no added stress in their life. The stools do not look like they contain worms but they both have the same symptoms that began yesterday. Can you help?