my broody's start their hatch between day 19 and day 23 generally. What tends to happen with mine is they leave the nest after the 1st born is 48 hours old. I've had some go back and hatch the remaining eggs, and others simply leave it to raise their little ones
Well hopefully with only 4 eggs the ones that are going to hatch will hatch in a timely manner. We will see. I have to move her eventually though or those chicks will fall out to a 4 foot drop.... :/