It's the Light Brahma hen's silver (black and white) coloring that produces red sexlinks. It's the same color as Light Sussex, Columbian Rocks, and Columbian Wyandottes. Breed isn't really important when it comes to sexlinks. It's the color genetics of the hen that matter. As long as the hen has...
Some birds feather faster, some feather slower. I've had slow feathering females.
This is picture of some of my Barred Rocks. Same age, same source. The chick on the right was very slow to feather in. You can see how her back was still downy and she hadn't gotten her tail feathers yet. The chick...
You bred non-typical red sexlinks. Since buffs have such pale down, it will be difficult at this point to judge which chick is silver-base color and which is gold-base color. As they feather in the males will have their mother's coloring. The females will have their father's buff coloring.