If your LO nursed less one day, would it be normal to notice a dip in supply the next?

My son got his 6 week shots on Thursday and slept most of the day. He nursed much less than normal. Yesterday, I pumped and had to work to get 4 oz from one side. I usually get 5 no problem. This morning on the other side I had the same problem.

Guzzling water today ! My supply is usually great so I don't want to start having issues