Decrease in drinking

Hey ladies,

I almost exclusively pump for my 10 week old, and do not supplement with formula. I've noticed that about once a week, or less frequently, my little one will have a day where she drinks half as much as normal. (Usually 7-800ml, down to 4-500ml, or of a 100ml bottle, she'll only drink 50ml almost all day long.)

Is this happening with anyone elses little one?