What? Wow! They have to be so tough to hatch out and then to die, that is weird!
Did they get chilled or not stay in the hatcher long enough? I can't imagine.
The only time I lose a little one is when tehy do not absorb the yolk well. Had a Marans do that last week. I left it in the hatcher for 24 hours but when I moved it to the house brooder it still had all that yolk it had not absorbed. I was pretty sure that was a doomed fate. And sure enough, 2 days later it died.
Right now I have 6 Xavier, 4 KK, 3 Fred and 1 Schmoozle chick in the hatcher. They are peeping and bouncing around pretty good. Some of the eggs were pretty nasty and I thought they may not develop or hatch but here they are. I had left them sitting for a while, too and thought they may not develop because of that but setting at home and going through the mail is very different.
I am sorry you lost them. I know that is very disappointing!