I just culled my cornish maybe 2 weeks ago.. So about 20 weeks. Dressed out between 9 and 11 pounds. Mostly did it because they are aggressive to my other ones about food and i wanted to stop going through so much feed. We eat them. Even brined for a couple days they were still tough and stringy.
I have 5 more about 5 weeks old. i had to add numbers to my hatchery order and wanted some i wouldn't really want to keep. These babies are also aggressive. Not quite sure why I have such a runt unless the hatchery messed one up. These are not going to last a whole lot longer.
This is why i go ahead with layer feed sometimes to strengthen their bones to help support their weight. I think for anything that needs nutrition balance is key and so is individuality.