I wish they came with guages too!! My DD also did this, I'm pretty sure around the 4 week mark too, only taking one side at each feed for about a week, then it upped back up to two. It confused me, but it seemed to be all she needed/wanted, and she only ever has one side through the night now, but drinks from both sides all day long. I've started to realise there are all kinds of normal when it comes to BF! HTH