Barred Rock or Marans?

[Percheron chick]

No. just because they were at one point bred to lay a certain shade of brown doesn't mean they still do. You appear to have at least eggs from 5 different layers in that carton. The darkest one looks like a welsummer and the lightest is the same shade as my CM.

 

[silvia32444]

Black sex links are all black with a very little of red (females).

 

[RoostersCrow HensDeliver!]

Black sex links are all black with a very little of red (females).

This is not true, they are hybrids so there is no limit to color variation. I have gotten a few mostly partridge colored sex links.

To the OP,
You have 2 Cuckoo Marans and a Black Sex Link. Even a hatchery quality BCM would not have that amount of gold leakage in her feathering.

If you are unsure of who is laying what, different food coloring applied to the hens vents will leave colored streaks on the eggs.

 

[BantamLover21]

The first two are Cuckoo Marans, and the third might be a Marans/Marans mix.

Agreed. Though the last one does look somewhat like a Black Sex-link. All are beautiful birds!