So sorry for your loss! Hmmm, maybe it doesn't work with mixed breed hens? I hadn't tried that... all the Silkie crosses I had hatched were by purebred yellow skinned hens... :/ I just relooked at your pics and looks like the black chick has yellow feet bottoms, that actually indicates yellow/yellowish skin... maybe the dark is the color of his muscle and not the skin??Unfortunately I lost the silvery colored chick and the black chick that seemed to have dark skin is a boy. Showing very stong evidence of bring a boy at just 3 weeks of age.
I've only tried it with pure Silkie roo and a purebred yellow skinned hen... all the dark skinned chicks were pullets and light skinned were cockerels... :/"dark skin means girl, light/yellow will be boy...« It's possible that dark skin chick is a boy. These three are mine, around 11 weeks old; mam is naked neck and dad is silkie; one dark skin is a girl, but the other one is a boy. The third chick is a boy, has no naked neck and yellow skin: this hen is from last year naked neck and silke dad: