If you will look at the eggs directly above the one to the left says 51.6(purebred Dark Cornish hen), you can't read the one in the middle, the one to the right says 60.5(Cornish Roaster hen) they all hatched. What I find is the smaller ones hatch early. I think it gets too crowded causing early hatch. They still survive. They are just smaller than my crossbred chicks. They fight at day two.
Nice looking chicks! I've found the Cornish chicks to be very scrappy and active too. They definitely grow up fast. Kind of odd for a slow to mature breed, that the chicks feather out and put weight on quickly. Much faster than my Buckeyes did, for the first few weeks at least and then the Buckeyes caught up and got ahead.