None are looking like definite males, but the first comb is pink. The fourth comb shows the least development. Everyone else is in between. I don't think it is enough to go on for accurate gendering. It will take more time.
Any dark breed can get the black combs and wattles.
This looks like a female to me at that age. If it is indeed a Mystic Marans, those are sex linked, so you're home free.
I could see it. Usually it is the male specific feathering that shows the leakage, so it may come later. Anyway, that is my guess based on the appearance of the chick.
I think the buff Brahma is the father. If the Deathlayer was the father, the pattern would be messier, and the chick probably would not have yellow legs. White skin is dominant over yellow skin, in most cases.
If the buff Brahma is the father, then the chick is a cockerel. Female chicks of that...
If she's broody then it makes sense. Many times I have had broody hens sit on eggs and raise babies together.
If she isn't broody then I would keep her away.
It is a myth. It is true that many European breeds with white earlobes lay white eggs, but this is something that has probably been selected for. White eggs were preferred in the past to brown or tinted eggs, especially in European countries.
Breeds like the barred Holland were bred to be dual...
The mother is a lot more brown than I would expect for Bielefelder x lavender Araucana.
I think the chick will be darker than her but will still have some brown. It will definitely be barred, like the Malines father.
The RIR and black olive egger look to be males.
The Rainbow is king of in between. I think it is probably a pullet.
The brown olive egger and the Wyandottes look to be females.