How quickly did you change his diet? The Innova should be fine, however I have heard reports of the Wellness causing issues with some... However I have also seen plenty of people report feeding it with no issue.
My recommendation would be to get some acidolphilus from your local health food store, and add a hefty sprinkle to his food daily for the next few days. You can also pull the Wellness to see if his GI improves after a few days as well. Limit all other snacks/treats to determine the nature of the GI upset. Limiting will also help settle his GI. If you don't see improvement or it gets worse, then schedule a veterinary visit and take a fresh stool sample in with you to have it examined.