wow! maybe someone else can hop in here... but I have read that humidity will not drown babies unless water vapor is condensing on the outside of the egg... that humidity just controls how much moisture is lost during the incubation process.... so low humidity means a smaller chick sometimes to weak to hatch and high humidity means a big fat chick to large to zip after piping...I can't incubate mine at all!
I have eggs in 3 different bators, have done all sorts of things to try and get them to hatch but all I can tell is that they are drowning and my humidity is reading 50%. I have had so many folks tell me to up to 70%! I can't get mine that high but there is no way I would even try. Every egg I open has a fully formed chick in it and lots of water. No shrink wrap, no pipping, just a dead chick (I wait 4-5 days longer).
However, my Silkie hens hatched out 2 for me.
But in the rush for everyone to be the mom one got squashed so I am down to one for now.
I have 6 more eggs under broody hens as i am sick and tired of trying to hatch them in my bators. Out of almost 50 eggs set I have one to show for it.
The pea breeder I got my hicks from just up ed his humidity from 56% to 62% and got almost a 20% increase in hatch rate...and he hatched hundreds at a time... maybe the babies are dieing of bacteria moving through the shell and killing the baby and preventing the absorption of all the liquid so it looks like they are drowning....
in my chickens I do dry hatches, and if I have a dirty egg or bad egg in the bunch.... a few chicks will do this... look to be fully formed when I break open the egg but be full of water... but I know they did not drowned as all other chicks would hatch normal