Awww... so sorry about your loss. How heartbreaking!! 
That's a really good picture of the eggtopsy you took. I'm not a chicken hatching expert--most of my hatches have been ducks and quail--so I'm not sure I'm right, but they look like they didn't quite make it to lockdown--just a little small, and a bit too much yolk. So for that reason, I hesitate to say that it was a humidity problem. But it is possible. And considering that they *almost* made it to lockdown and that the air cells were small, try hatching dry next time. This will allow those air cells to develop more fully--I would suggest this for you, regardless of what the actual cause of death was, because with underdeveloped air cells they are likely to have died at hatch time anyway.
What happens when the air cells are underdeveloped is that the babies can't push their beaks into it and get their first breath or, if they do, there isn't enough air or they can't keep their beak high enough to keep breathing (once they take their first breath, just like human babies, they MUST continue breathing) and they drown.
Could it be there was a temp spike right after you candled? That will kill chicks pretty quickly and at about the same time. Sometimes with homemade or low-quality incubators, the thermostat gets confused when there's a sudden influx of cool air, and sends the temp soaring before it can adjust again.
Don't give up! You got so far, and next time will be easier. Keep us updated!
That's a really good picture of the eggtopsy you took. I'm not a chicken hatching expert--most of my hatches have been ducks and quail--so I'm not sure I'm right, but they look like they didn't quite make it to lockdown--just a little small, and a bit too much yolk. So for that reason, I hesitate to say that it was a humidity problem. But it is possible. And considering that they *almost* made it to lockdown and that the air cells were small, try hatching dry next time. This will allow those air cells to develop more fully--I would suggest this for you, regardless of what the actual cause of death was, because with underdeveloped air cells they are likely to have died at hatch time anyway.
What happens when the air cells are underdeveloped is that the babies can't push their beaks into it and get their first breath or, if they do, there isn't enough air or they can't keep their beak high enough to keep breathing (once they take their first breath, just like human babies, they MUST continue breathing) and they drown.
Could it be there was a temp spike right after you candled? That will kill chicks pretty quickly and at about the same time. Sometimes with homemade or low-quality incubators, the thermostat gets confused when there's a sudden influx of cool air, and sends the temp soaring before it can adjust again.
Don't give up! You got so far, and next time will be easier. Keep us updated!
