Bielefelder x Black Australorp, still solid black with the white belly. Same with the Bielefelder x Jersey Giant cross. The black seems to overpower all other colors for newborns.
A Blue Australorp chick
If you look at your speckled sussex chick you can see that the third has the same...
https://www.backyardchickens.com/threads/show-me-pictures-of-your-mixed-breeds.1599867/
I should have another group hatching in the next few days. Father is Bielefelder in all cases, mothers could be Jersey Giant, BA, or RIR.