I, personally, never mess with bringing humidity down at hatch. Prior to going into the hatcher, yes. After incubation is pretty much over and the first eggs have pipped, no. I am guessing you want to do so because the eggs have not lost enough weight? If so, I have never seen that reducing the humidity at hatch helps much or at all. That is why it is important to monitor air cell size during incubation. By hatch time, it is usually too late in my experience. YMMV and others may disagree. That is just my experience.