Because you have been hatching for years might as well ask a couple questions! If that's okay. After they hatch how long do I feed them medicated chick starter? The day I put them in the incubator does not count as 1 out of 21 days? The temp is exposed to be at 99.5? Thanks.
I had opened the air cell end of the egg when it was the last egg with no pip and noticed the shallow breathing and hatched the chick manually. He was still breathing during pictures and stopped breathing before pics were done.
There is always risks to hatching. I've had a chick with a prolapsed umbilicle that I had to cull. Also a mostly blind chick I kept. A chick with curly toes(that was probably a humidity issue on my part.. that was my first hatch!
I've always gone by if you put them in the incubator before noon that is 'day 1'. Also I dont feed medicated chick start. I feed plain (un-medicated) flock raiser.
Good luck!
ETA: I've also noticed the ones you help sometimes have the most problems. I no longer help a hatch because thats how I ended up with the little blind one.. If they're not strong enough to make it out of the shell they dont make it in life.