Stiletto
On the other side of the road
Look up Ayam Cemani chickens. They’re very rare and it’s possible that one of your hens carries the gene for their melanosis (I think that’s how it’s spelt). If you look at your ladies and see who has dark red, dark brown, or even black earlobes you may have your culprit! If this is so, the eggs are perfectly fine to eat and may only occur once in a blue moon, so hatch the eggs to carry on the genetic mutation! Or eat the egg and treat yourself!
Ayam Cemani eggs are not black - they are light, a shade of cream.