If you're in the egg biz and you have just one breed, make sure the roosters you keep are the same breed as hens to keep your lines pure. It makes a big difference in egg size, color, quality, and production. I had some leghorns that free range with "other" roosters and I hatched a bunch of their eggs. The babies were cute but grew up to be horrible egg layers plus the egg size went way down. Cute doesn't make money in the egg biz.
I'm starting to come to the conclusion that it matters more who the rooster's mom was and how productive SHE is/was.
Chickens are opposite of humans. Human females are XX and males are XY. Chicken females are ZW (the rough equivalent of XY) and males are ZZ.
In any mating, a pullet will get her one and only Z (our X) copy from the rooster, and the hen will only contribute a W (our Y) to that same pullet. Therefore the rooster is the sole source of the "Z" chromosome to all of his daughters, and that Z chromosome has a lot more "stuff" on it than the W chromosome does.
Of course, the rooster has two Z's - one from his mom and one from his dad - so his daughters could be getting either one. My point is - the leghorn hens that laid the eggs you hatched couldn't pass on her Z (X) chromosome to her daughters, which might account for the disappointing laying of the offspring. If one of the leghorn hens' sons was used on the flock, he would be the sole vessel for distributing her Z chromosome to offspring.
It's a lot like heart size genetics in horses. Secretariat had the famously gigantic heart. None of his sons had the large heart gene (from him, though it appeared in other lines when they tested for it), much to the chagrin of those who bought breeding shares --- because (as it was later discovered) the large heart gene was carried by his daughters on the X chromosome. He could only give his sons his Y chromosome.