Oh no! I'm so sorry! It sounds like you usually kept the humidity nice and low through incubation but if you had fluid build up in the air cell then it was definitely too high. 80-90% can definitely do that if left for extended periods of time unfortunately. If they weren't internally pipped it wouldn't be from drowning though. Did it look like there was a sort of sticky goo around the chicks?
I didn't break the membrane because they really stuck and I didn't want to make them stink more but there wasn't water in the air pocket if that's what you were talking about but when I like push the membrane it felt like a plastic bag filled with water and a chick inside