I understand. It can be a mystery. One thing that stands out to me is that the successful hatch came from shipped eggs. The poor hatches came from your birds' eggs.
I feed them 16% laying crumbles, occasionally Purina game bird chow, oyster shell, leftovers from my garden, and whatever they get free ranging. They free range my 40 acre blueberry farm from daylight to dark. I’m in north Florida, so we don’t have cool weather until right now in mid November. Abundant insects and browse.
One of my Florida Cracker game hens just had a nice hatch. She is my first hen in this flock to set. I also sent a couple of dozen eggs to the University of Florida for one of their agg programs to hatch. I’m awaiting to hear how those did.
I’m reasonably sure its a ventilation problem. I’ve spent a lot of time since my initial post studying incubators on Youtube and it seems like most have quadruple or more times ventilation holes and larger size than this incubator has. To the point that my incubator seems ridiculously sealed in comparison.
Given that 2 chicken egg hatches were on time, I'm guessing that temperature wasn't the problem.
I highly recommend that you revisit the nutrition of the breeding flock.
Layer feed is sufficient to produce eating eggs but some of the vitamins and amino acids are too low to produce eggs with good hatchability.
Some feeds could contain methionine as low as .4% or less. For viable hatching eggs, it should be .5 to .6.
Lysine should be at least 1% and Cystine should be at least .75%.
Vitamin A should be at least 5,000 IU per pound. Many feeds are about 3,000.
Vitamin D should be 2,000 to 2,500 while most regular feeds contain about 1,000.
Vitamin E breeder feeds levels need to be over 50 i.u. per pound while non-breeder feeds are often at a level of 20 IU per pound.
These enhanced levels of nutrition should be made to the flock's diet about 3 weeks prior to collecting eggs for hatching.
Layer feed is for laying eating eggs. Breeder feed is for producing hatching eggs.
