Plants drinking less during flowering?

During the first few weeks of 12/12, it seemed I was replacing about 2 gallons per day in the res, and now (day 29 of flowering) they only seem to drink about 1 gallon per day. Is this weird?

Also, for a while it seemed like quite a task to keep the pH in check, I was having to adjust it maybe 2-3 times per day. Now, it seems like it stays much closer to where I want it, and I only need to adjust once per day, if even that.

Are either of these things cause for concern?

Thanks for reading, here's a few pics for fun.

Yeah they dont need watered as much because the lights arent on all the time.