you need to keep humidity 40-50 % during 18 first days, and bump it up to 65-75% during last 3 days (19,20,21).
during first 18 days, we lowering humidity to make sure there is enough space for embryos to grow, because we need to vaporize the volume of liquid inside egg, you can see it by candling, the air sack is bigger and bigger. if humidity high in 18 first days, the embryos will be drown and dead and we don't want it happen.
and during 3 last days, we increasing humidity to high in order to make the egg shell easier to be break by the chick when he want to get out. if you don't increase humidity on last 3 days, you will find that the chick hardly to get out of shell and even dead in shell.
and now after you know why and what, then you will know appropriate action to be taken for your eggs, good luck and godspeed.
