The most important questions are which hens laid the eggs that hatched and which rooster was it that supposedly provided the sperm? I realize that this runs against all beginners logic but too many roosters or cockerels is more detrimental to egg viability than a few tenths of a degree in temperature.
Seeing that your eggs set on the kitchen counter for X number of days before being consigned to the incubator, just how often were they turned before incubation began?
I cannot think of a worse place to store eggs than the average kitchen.
Besides the swings in temperature there are numerous DANGEROUS (to an egg) chemicals present in the air. Set a fresh laid white shelled egg on the counter and near the stove and observe how bacon grease or other cooking residues find their way onto the shell.
A stand mixer, or even and electric can opener can create enough vibrations to addle the contents of an egg before development can begin. This is without adding any radiation leakage from a microwave.
Eggs that are 14 days old are starting to push viability some and any egg that is older than that is generally a lost cause. Furthermore, viability begins decreasing the moment the egg is laid.
We have yet to get into the subject of the age of the hen who laid the egg or of the rooster who supposedly fertilized it, or how healthy were the prospective parents, nor have we touched on the subject of flock diet and its affect on fertility.