I posted pictures of these guys (hopefully girls) several weeks ago to try and determine what they may be. Im still not sure so I thought I would post these pictures since they are now fully feathered. They all have single combs and are almost 9 weeks old.
They look nothing like black sex links to me. I think the others are going by the very general coloring that you get by crossing a black chicken with a colored chicken(which is what black sex links are) but that goes for ANY breed and is not limited to black sex links.
They look like backyard mixes with something pencilled or laced... with the presence of that cornish looking(second pic) I would guess probably dark cornish mixed with different breeds.