Sour Milk / Reflux

My baby is 7 weeks - she doesn't have bad reflux, not much spitting up, but she does seem to get milk residue on the back of her tongue. It seems like she's trying to move her tongue to wipe it away, she will make a sour face and sometimes even seem to be 'chewing' or working on what's left in her mouth. I can tell it's unpleasant for her and I'm guessing it doesn't taste good. Anyone have this or know how to help her out? She's EBF.