J.S.
Are you giving him the ones with the extra iron in them? Because the original ones don't have iron in them. Nor do they contain sugar or any artificial colors. My guess would be that he could be constipated from the extra iron he is getting. Iron constipates really bad. My kids could never eat the rice cereal or any of that baby stuff with added iron. And my oldest gets very hyper when she is constipated, she is just so uncomfortable. You could try giving him a little pear juice everyday to help keep him going. Or maybe don't do the polyvisol with iron everyday. But that would be my guess as to why his behavior changed from the vitamins.