UPDATE - The Good, the Bad, and the Unknown
As of this morning, I have 1 strong healthy chick who hatched perfectly yesterday.
The three other pippers died in the shell overnight without making any further progress. I thought one had zipped yesterday but it turned out to be a line of goo around the egg from the first chick's hatching.
"Eggtopsy" revealed two of the three chicks were extremely large - bigger than the one that hatched! One was in the proper position (it was the second cheeper). The other two, who had pipped closer to the pointed end of their eggs, were totally upside down and their heads had not turned into position for zipping. I'm surprised they managed to pip. All three had been "rocking and rolling" a lot yesterday. One of the "breech" ones had a burst yolk but its head was straight down on top of its belly -- maybe it broke the yolk while trying to pip? All three pippers had pipped externally and had air, so did not drown.
Lockdown humidity was 70 to 75 percent (I had purchased a hygrometer and put it beside the eggs-- had been warned not to trust the indicator built into the bator)
Despite the humidity, could the membranes have dried out? Or could the chicks have been simply too big to move around?
I candled the remaining four eggs left in the incubator that hadn't pipped. Three had not developed. One has developed and is moving, but appears to need a few more days. It would be nice if that one actually made it so the first chick won't be lonely. Meanwhile, I'm looking for some day-old chicks so I can put one or two in with the survivor.
I'm naming the healthy chick "Harry Peeper - The Chick Who Lived"!