Poo Q - does infant gaviscon affect lo's poo (sorry if tmi)

For weeks and weeks Archie has had green runny poos, almost always just once a day but sometimes twice. But since I've changed his milk from easy digest to normal Aptimal 1st formula and added the gavison (he has reflux) he poo's sometimes 3 times a day and it is yellow, like mustard. But quite solid. Not rock hard but definitely more solid than ever before. I don't think he is in any pain, although he does strain more than he used to, but just wanted to see if anyone else had noticed similar change due to gavison? Or am I blaming it on the gaviscon when it could be something else. Thanks girls. S x