Help need advice

Chloe

My baby is 3 1/2 months old now she is eating 4 to 5 oz per feeding. I started ro notice last week, I was only pumping 3 oz instead of 5. Now I'm only pumping 2 oz eat time. Ive upped the times I pumped drinking alot more water and no changes anyone have any tips to help get it back up?