The late hatches are almost surely telling you your temps are to low. They're not developing like they should, or at the rate they should. The longer they are in the incubator, the tougher the membrane gets, and the tougher the shell gets. Therefore, making it harder for them pip. Both internally and externally. An additional calibrated thermometer or two inside the incubator should help you know the correct temperature. Alot of time the built in thermometers on the incubators are inaccurate. I have better hatch rates with my temperature at 100.5. If your incubator temperature is set at 99.5, chances are its cooler, and chances are its even cooler than the ambient temperature inside the eggs. Your humidity isnt no where near as important as correct temperature. I have better hatch rates with dry hatches. Here in missouri in in my house, running dry keeps the humidity around 35%, depending on weather and season. But yes, as someone mentioned before, the room the incubator is in, the rooms temperature will affect the incubator temperature. Its recommended to keep the incubator in a room where the temperature stays at a certain consistent temperature, and away from drafybareas and direct sunlight.
