hatching silkies

[Penny3445]

I have 2 silkie eggs one hatched on day 21 and the other one isn't even pipping yet ( day 22) so I took it out to candle it. I can't see a air sac but I can hear it chirping, so I returned it to the incubator the humidity dropped to about 50% for 20 min. Do you think I killed it and if not how long should I wait to make a external pip? Can it breath if I can't see a air sac? This is my first time so any info would be great. Thanks!