I wouldn't jump to the conclusion of the white one being mixed, she's probably just a result of generations of not selecting properly feather stock. She appears to just have very light leg feathering. Since she is silked, she's not an F1 mix. I'm not ruling out that there could have another breed somewhere in her line, but she at the very least has quite a bit of Silkie in her. Hatchery quality Silkies are extremely variable in quality, not necessarily from mixing breeds, just by not culling breeders that don't have the correct traits. As for genders, the White Silkie looks like a pullet and black a cockerel 
