They're supposed to pip - absorb yolk and blood - zip - pop. Pip to zip might take hours and hours (but no rule - they can go fast, they can go real slow).
Post a picture for the experts to see + see if you can see movement from behind the pip (a moving beak).
A question for the experts; Assuming that humidity was too high for the first three weeks, isn't it too late to correct that now? And; if humidity were too high for that long, wouldn't that mean that the chicks wouldn't be able to pip? I.e for the one(s) that
has pipped, possible high humidity should NOT be an issue?
From what I read 70% is on the high side + once one hatch it will rise further (temporarily). If you have seen condensation/fog at any stage while at 70% then maybe the reading is accurate (if so ideal would be to reduce it to 60-65%).
If you have NOT seen condensation/fog at all - at any stage - while it has been reading 70% all the time, then the reading might have been to high and your real humidity might have been closer to what is normally recommended. In that case you do not want to reduce humidity.
Hopefully some experts will chime in, but I (as a noob that is) would say keep as is and watch what happens once your current pip hatches (in 0-24 or more hours). If you get condensation/fog when that chick dries, your reading is probably accurate. If you do NOT get condensation/fog when it hatches, then your reading is probably too high (they might be of by a lot).