By the time they're pipping and hatching you really don't need to worry about humidity spikes or even extended periods of high humidity. If your humidity has been good the first 18 days, you should be fine now. I sometimes hatch with 85%+ humidity and the chicks still pop out and dry off just fine. High humidity at hatching will NOT drown your chicks. It just doesn't happen that way. What causes chicks to drown is when not enough moisture has been lost from the egg throughout the entire incubation process, and the chick inhales the excess fluid that is still INSIDE the egg. It's nothing to do with high humidity at hatching time.
P.S. That is a really funny photo. Very cute chick!