Yes! That's the correct way of editing information: updating an existing object if you think that it's missing some properties, or changing those properties if they are wrong.
Creating an additional object with those properties only makes an impression that there are two objects in reality, not one. So it's just wrong.
By the way, is this dairy shop also a correction of the already added convenience store, or is it another shop in the same building?
https://www.openstreetmap.org/node/12110140269