Right breast producing less

Noor

My second daughter is now 10 weeks and I breastfed my first for 13 months, I’ve always had my right breast produce more milk than the left. For some reason it is no longer giving me as much as it usually does, so instead of giving me around 3-4 ounces it’s around 2-3. No changes to my left side, it’s producing the same amount as the usual.

Can anyone explain this?