Aw, it's okay - you'll get him settled back in
. Stop all treats right away. Get him back on the Newmans immediately - since he had no upset while on that food. And then, if you *do* want to switch to a different food long-term - you'll want to choose based upon the things might be common ingredients in the foods that are causing him upset. In other words - look at that bag of treats - what's in there? If you give us the exact name of those treats, some of us can take a look and might be able to guess at what might be common to the treats and the other 2 foods that could be upsetting him - compared to Newmans.
Also, he's not a puppy is he? He's an adult? If he's a puppy, there could be some other things to check out at the vets.