i thought the same with our broody as she kept returning to an empty nest after going for a run outside, and found the eggs on day 3 stone cold, we had the same hatch sequence, but we didnt note when they would hatch, we said saturday sunday or monday of the 3rd week and 5 hatched saturday 1 sunday last on tuesday or wednesday, but there was so much nest activity that it died due to injury, sad to say i had saved it 3 times through the day, and had spent time warming it in enclosed hands, but i put it back too early, i thought they had settled for the evening when i put it back under, hoping the next day it would have been walking about and strong enough to fend for itself, but i heard cheeping 30 mins later and everyone was out the nest with the late hatcher half buried and visibly injured in the nest, it was still alive but struggling, so i put it in a cool place and let it die peacefully.
next time we get a broody we will be getting a small brooder for just such an emergency, we can only but learn from our mistakes and experience comes from learning. we didnt expect to have a chicken go broody less than a month after she 1st laid an egg, we have only had chickens for about 4 months. its been quite an experience.