Your unhatched chicks will not drown due to 90% humidity at this point. If your humidity has been correct throughout the incubation and your eggs have already lost the correct amount of moisture, they'll be fine.
Chicks drown inside their shells when your humidity has been consistently too high throughout the incubation. They don't lose enough moisture, and when they break through into the air cell to start breathing air, they drown in the excess fluid still inside the egg. Because they're alive up to that point, and then they die during lockdown, people mistakenly assume that it was the high lockdown humidity that caused them to drown, but that's incorrect thinking.
I incubate at 40-45% humidity, and hatch at 75-80%+. Once they start popping out, the humidity often shoots up past 90% and stays there for ages. I just leave it be, and they're always fine...