Decrease in milk supply

Ginna

Have any mom's noticed a decrease in their breast milk supply after 7mths. I just noticed a decrease in the amount I am able to pump when I am working. I usually was able to pump 4-5oz during each pumping session, now only able to pump 3oz. Should I start drinking mother's milk tea. My son drinks 15 to 18oz when I work, I am away 9hrs.