You probably already know all this but I’ll go through it anyway.
First, there is nothing magic about hatching being exactly 21 days. Often it is not. There are a whole lot of different reasons hatching can be days early or late, heredity, size of eggs, humidity, how and how long they were stored before you started, many things. A really big one is average incubating temperature. If your average incubating temperature is warmer, they can be way early. I’ve had some pipping when I went into lockdown and hatch just a few hours later. If your average incubating temperature is a bit cool, they can be that much late. And different eggs can be different. Especially in a still air incubator, the temperature can be different in different parts if the incubator.
You have to count the days correctly to know when it has been 21 days. It’s pretty normal for people to get that wrong. An egg does not have 24 hours’ worth of development 2 seconds after it is put in the incubator. It takes 24 hours for the egg to have a day’s worth of development. An easy way to figure it out is that the egg should hatch on the day of the week you started them. For example, if you set the eggs on a Tuesday, they should hatch on a Tuesday.
But should hatch does not mean they will hatch then. Go back to my first paragraph. The hatching process is so random that you don’t have to be that precise with lockdown or many other things. Most people can lockdown a day early and still get a good hatch. Those eggs are generally pretty tough. You don’t have to get it exactly perfect. You just need to be fairly close.
Hatching is not an instantaneous process. The chick internal pips, external pips, then finally zips and pops out. There is a lot going on during this time. The chick has to learn to breathe air instead of live in a liquid environment, absorb the yolk, dry up blood vessels external to its body it no longer needs, do something with that gunk it is surrounded in so to dried nice and fluffy instead of all matted down, and who knows what else. Some chicks do most of this before external pip. These pop out pretty quickly after external pip. Some do a lot of this after internal pip but before zip. These seem to take forever. Some even zip before they are totally ready. Many of these make it anyway.
If you try to help a chick before it is ready, you can do harm to the chick. Many you try to help die. I strongly encourage patience.
As to removing the hatched chick, I would not. You don’t have to. Since it absorbed the yolk, it can live three days or so without food or water. That’s why they can be sent in the mail. A lot of people freak out when they see the early chicks playing rugby with the other eggs. As far as I am concerned, that is not a problem. I’ve had many eggs hatch that were rolled all over the place before and after they pipped.
If you open the incubator to take that chick out you run the risk of shrink-wrapping chicks that have pipped. That is where the membrane dries out and shrinks around the unhatched chick to where it can’t hatch. It’s possible the pip is down at the bottom where you cannot see it, especially if a chick has been playing rugby with the eggs.
There is a difference in what can happen and what will happen. I did not say you absolutely would each and every time without a shadow of a doubt shrink-wrap a chick. I said it might happen. I’ve opened the incubator before to deal with an issue. I’ve shrink-wrapped a few eggs doing that. I’ve also had a lot that did not shrink wrap. There is a risk so I suggest you not take that chance unless you have a reason to.
I don’t know what happened to your previous hatch or why you determined it was a humidity issue. This link is something I’ve used to try to determine how to help my incubation. It may be useful to you. Good luck!
Mississippi State Incubation Troubleshooting
http://www.poultry.msstate.edu/extension/pdf/troubleshooting_incubation.pdf
I would not try to drop the humidity at all. Humidity can be different for all of us, but my minimum humidity is 65% for lockdown. After they start to hatch the humidity can climb to 85%. They hatch fine in that.
