Quote: Ok I will look for patterns when I turn off this time and test the temperature and hr as you advise.
Yes I have opened the eggs in the previous attempts and based on images I googled my guess is most of them (say 70%) died between 18 and 21st day, and by checking my notes posted here a couple of persons agreed that hr was too high and now I know they are right, so I believe they drowned, I will open unhatched eggs this time too and will try to be a little more carefully with my notes and observations.
You are right about humidity drop, I remember that it was more than 10% and it took about 15 to 20 minutes to recover I think, but by that time there were no pips, now I have a new concern, as I mentioned before one chick will be 48 hrs this afternoon and my wife just called and told me that 2 more just hatched, and 2 more seem to be piping, how will I take the old one out without killing the ones piping?