John definitely lost weight during that period. Wasn't '66 his "fat Elvis" (his words) period? So he gained weight between 1964 and 1966 and then was noticeably thinner in 1967. Weight loss in his face would also make him look older.
Paul has a cap on one of his front teeth. There are photos from about 1966 where it's not there. So maybe his teeth looked slightly different after he got the cap replaced.
Who cares? Paul is a rabbit, naturally. And John had always wanted to get thin. So nothing to see here. Ho-hum.
Today, it's unthinkable that a pop band would pose for photos with one band member showing off his chipped tooth, but the Beatles did.
You honestly think that in this age & era people would care about a tooth cap? It's a freak show nowadays, jus' look around. The young 'stars' do the whole sesh of weird posing/mimics. Because it was hippie time in mid-60s doesn't mean it was an epitome of freedom. That whole hippie stuff is so laughable, what with the clothing & hilarious pacifist thoughts.