Bright yellow legs with a dark wash down the front is correct for BR pullets. Cockerels will often be lacking the dark wash. From what I see from your pics, all is correct for those birds to be BR.
They look very much like hatchery BR to me. Why do you think they aren't? It's normal for BR pullets to be dark and cockerels to be light, and for BR to lay lighter-brown eggs.
I agree. I added a couple of hatchery Cuckoo Marans to a chick order once on a whim, and I didn't get eggs that looked different from any other egg in my flock. Also, the hens were just plain stupid, and stood there looking at hawks after the rooster gave the alarm and all the other hens had...
I think your Marans mix is a pullet, but she's got a very developed comb for only 16 weeks. My Marans combs have only just started to redden up in only some birds, and they're 19 weeks old.
Give that hatchery hell!
If it were me, a very irate phone call to that hatchery would be my first order of business this week.
That "hatchery" doesn't seem very professional if they'd send you mixes instead of what you ordered.