Poor Harley.  Glad you had your vet check him.  How much does he weigh and how much do you feed him per day?  Does he get any additional food or treats?     
Do you give probiotics or plain yogurt?  Sometimes these solve tummy problems.     
Has he always been on Wellness?  I have read a number of cases on this site and others about Wellness/vomiting.  It's a great food, but it may not be for every dog....even if they have been eating it for some time.     |