Eggs can be left at room temperature for up to a week while acquiring enough for a full cluth to incubate. Less is preferred, longer greatly reduces the chances of success. Also, if the eggs weren't stored pointy end down during this time, that lowers odds, as well as the movements in between...
Then it sounds to be previous environmental or genetical factors and unrelated to your actual incubation process. Sounds like youre doing it perfectly!
Well knowing how long the clutch sat out before being incubated is a factor in viability. Also, the temperature of where they waited. (Fridge, room air, etc) if they were gathered from the nests and immediately went to incubation, it probably is at a contributing issue. Also, just simple...
You need additional calibrated thermometers aside from the actual installed incubator thermometer. They are notorious for being inaccurate. It could be 1 degree cooler than what it actually reads and that is disastrous. Aside from temp verification, it sounds like you're doing everything right...
Temperature really depends on the individual incubator. Eggs must keep atleast a 99.5 internal temperature to develop properly, and that is the minimum. If your incubator has cool spots or fluctuates temperature or other varying factors, higher temperatures are probably more sufficient. I like...
I dont see any indication that 1, 2, or 3 are viable. 4 seems to be ok. I find it much easier to get photos shining the light from above down onto them. It also prevents turning them upside down to much risking detatching the air sac or rupturing the veins. How are you hatching? Incubator...