You need to calibrate your thermometer and hygrometer to know what you are actually dealing with. Factory presets are not always right with any incubator or any instrument you may buy. These might help.
Calibrate a Thermometer
http://www.allfoodbusiness.com/calibrating_thermometers.php
Rebel’s Thermometer Calibration
http://cmfarm.us/ThermometerCalibration.html
Rebel’s Hygrometer Calibration
http://cmfarm.us/HygrometerCalibration.html
There are many different reasons eggs may be as much as a couple of days early or late. It’s not always temperature but temperature does paly a big role. Since yours are pipping about on time, your temperature is probably pretty close.
Humidity is a lot harder to talk about than temperature. For many different reasons different humidities work for different ones of us. That’s more of a trial and error type thing. Even the professionals that use incubators holding 60,000 or more eggs have to do some experimenting to find the optimal humidity for that specific incubator in that specific place. Just moving that incubator across the room can mean you need to re-tune that incubator to find the sweet spot. The good news is that you normally have a wide range of humidity that works pretty well. You don’t always have to hit the humidity perfectly. That sweet spot is fairly wide.
Now to your particular situation. Before a chick hatches it has to do a lot of things. It has to absorb the yolk, dry up blood vessels it no longer needs and absorb that blood, do something with that gunk it has been living in so it dries nice and fluffy instead of the down plastered down, learn to breathe air instead of live in a liquid environment, and who knows what else. Some chicks do a lot of this before external pip. These usually don’t take a lot of time before they zip and hatch. Some wait until after external pip to do a lot of these things. As you know this can drive us crazy with worry. I’ve had several take longer than 24 hours after external pip until zip and hatch. Usually when a chick starts to zip it finishes and hatches but often they will stop to rest a bit before continuing. It is really hard to know when a chick is in trouble or if it is just slow. One absolutely sure sign. If you see a yellow fluid coming from the pip hole the chick is in big trouble. You don’t have any time to waste.
It is possible that you can shrink wrap a chick by opening the incubator after external pip. It is possible but that does not mean it happens each and every time. Often it does not happen but since it is possible it is best not to unless you have a strong reason to do it. That’s just good practice. That dry membrane doesn’t have anything to do with temperature, it’s due to humidity, both during incubation and during lockdown.
Since you have opened the incubator I suggest you take that egg out. When you open the incubator to do that, lightly mist the other eggs with lukewarm water to help keep them from drying out. Don’t soak them where you drown the chick but just a light mist. Then after you close the incubator, carefully start to take the shell off. If you see any blood, stop immediately. Slowly and carefully. Blood means the chick has not absorbed the blood vessels and is not ready to hatch. Mist the membrane and put it back in the incubator.
If it does not bleed, very carefully remove the shell and the membrane. If the chick is alive, dunk it in a cup of warm water (lukewarm, around 100 degrees) to rinse off some of that gunk. Do not put the head under water so you drown it. Just rise the worst of the gunk off. If a few small chunks of shell still remain, that’s not a big deal. All you are trying to do is rinse enough gunk off so that the chick can move once it dries off. Some down will still be plastered down when it dries. That’s not a problem, it will go away in about a week. You just want the chick to be able to move when it dries. Then put the chick in the brooder under the light so it can dry off. Be careful not to chill the chick getting it to the brooder.
Use your judgment on what to do with the other eggs.
A lot of chicks that we help don’t make it. They may just not be strong enough to hatch on their own even if conditions are perfect. They may have something wrong with them internally. We may injure or chill them by trying to help. I wish you luck!
