We just hatched our first chick ever yesterday!
All the way until lockdown we had 70% to 60% humidity. Oddly enough, opening the windows (of the house) and keeping the two top vents closed (it's a GQF Hovabator with fan) brought it down to the low 60's for us. We've had the 2nd coolest spring on record with probably about 9 days of sun since January, so the weather here has been the pits. I was so worried about the chick.
I thought...since we had high humidity through the first 18 days, I would let it stay at 65% during lockdown. NOPE! Needed to be in the 70's since the chick was showing signs of drying out. We did help it out (just to get it's face clear of both membranes then it did the rest of the work) and it's doing just great. But did need a little bath to help get off the inner membrane that had stuck to it in some places.
SO! I would say not to worry about it, make sure you have good ventilation and air flow and just watch that the air sacs do get larger and larger. Also, be prepared to help out ones that are too gooey.
We ordered large silica packs (4"X6") and they didn't work for us -- actually raised the humidity because they were DRAWING IN HUMIDITY through the one always-open vent hole.
If anyone wants them for something else, let me know!