I hadn't put that together with his new height, I bet that is what happened - though it still bugs me that no one seems to have noticed ("Gee, Ed, have you grown a few inches?").

Being a walking philosopher's stone has to have messed with Hohenheim's DNA, it would make sense for Ed and Al to be affected. Chances are Arakawa's not going to take the storyline that far forward in the manga, though.