Are you talking about the chicks not having red feathering on their necks? That has a lot to do with the father breed. I used a Black Cochin over my Dominiques and 3 of my 4 pullets are all black. The one that has red on her had a Dom/RIR mother.
I've had 2 batches of black sex links. My first batch looked like yours, with very little red, and one practically didn't have any. The batch I have now has soooo much red! Even in their tail feathers! I think it just depends on their parents, and luck of the genes.