As always, humidity is a matter of opinion and personal experience. I run all my lockdowns at 75%+ and have never had a problem with it. If your humidity has been good throughout the incubation and your chicks have lost the correct amount of moisture by day 18, you can pretty much have your lockdown humidity as high as you want without any problems. I ran one lockdown with humidity up past 90% for a day and a half, and the chicks hatched perfectly and still managed to dry off in the bator just fine. That was in a fan assisted bator though. I don't think they'd have dried off very well in a still air bator with less air exchange...
If one of yours has started to zip, that's the clearest sign possible that your humidity is okay. If they can zip, they're not stuck! Sounds like they're doing okay. Just resist the temptation to open the bator and help ones that don't seem to be making any progress. Good luck with them all!
