The black one does look like a Black Copper to me. Just because she has no other colors yet, doesnt mean she is a Black. She may get some color, or she may not!
There again, I know nothing about the Black Marans, othere than they exist and are not a Black Copper...
the black one is not a marans because of the eyes and beek colors are not the right is my un edgucated guess lol , heck i know nada ,,,, im a carpenter giveing chicken advice .... but they are nice looking birds