I forgot to mention something. Around the 20th day (which was a Sunday), at 7 in the morning, I opened the incubator, turned the eggs, and unplugged it from the socket. I intended to ventilate the eggs for 15 minutes and stepped away (as I planned, for about 5 minutes). I came back in the evening (around 5 PM) to turn the batch, only to find the incubator open and unplugged from the power (I forgot about it for 10 hours). The eggs cooled down to 24 degrees, which upset me. But as it turned out, this didn't affect the hatching much: 35 chicks out of 36 eggs hatched. That's the story.