With light roasts, from my own experience, aging does play a big role. The sweet spot becomes more evident. Either too fresh or too old won't taste great. Darker roasts are more forgiving. I use to wait at least 5 days post-roast to start pulling espresso shots, and I also try to consume it within 1 month.
Back to the OP's point, maybe if the first shot is being pulled right after the 2-3 days old bag has been open, and the next day shot has considerably dryer grounds (that will depend a lot on local humidity and how the beans are being stored), then I also think it's possible this might be the cause.
A good test would be checking further, on day 3 and see if big adjustments are again necessary:
Day 1: open bag, dial grinder, make note of grinders setting.
Day 2: re-dial grinder as necessary. Make note of adjustments
Day 3: re-dial grinder as necessary. Make note of adjustments
If on day 3 there are again major adjustments required, I would stop thinking about beans freshness and would look into something else (grinder alignment/calibration, distribution/tamping technique, etc)