There's a learning curve with hatching, don't beat yourself up for doing the best that you know - just continue to learn better. When I hatch chicken eggs for the first 18 days I keep the humidity between 35 - 40%, days 18 to hatch I kick it up to about 65%. IMHO, lot's of people incubate at much too high of a humidity level. BYC member, Pete55, has an excellent thread on hatching and I've quoted a small portion below. The thread is a sticky on hatching waterfowl on the "geese" section, but much of the information (NOT the specifics of temps and humidity) can be generalized to other birds. It's a very informative thread.
This quote pertains to the reason for many late stage incubation deaths, it's Pete's assertion that the chick does not literally drown in excess fluid inside the shell (after internal pipping), but that the excess fluid accumulation is
internal: and caused by inadequate moisture loss (too high humidity) during incubation.
"It is in this phase of hatching that many chicks die resulting in late dead in shell. It is a time of great stress and physiological change within the chicks body. The heart is pumping rapidly due to exertion and trying to compensate for changing blood gases. It is my opinion that inadequate moisture loss during incubation causes the chick and its supporting cardio-vascular system to be overloaded in fluid. With the heart having to pump faster and harder to compensate the chick goes into heart failure. The tissues in the body become swollen with excess fluid (oedema) and the chick weakens. The space for manoeuvring into its hatching position becomes even tighter and the chicks body is simply too weak to withstand the vital changes required."
I would really recommend Pete's thread to anyone interested in learning to hatch.
Good luck with your little ones -- don't give up!