I am a newbie Marans person

I started a thread under the "what gender is this" but am hoping it is not bad etiquette to also ask the question here from the marans experts? I bought two "sexed" BCM babies but they have a lot of colour already at three weeks old, and from everything I have read here that is a typical roo sign. However, the two chicks look very different to each other - one feathered out fast (it has coppery flecks through all the feathers and a slightly pinkish comb) and the other still has stumpy wings, but they are copper at the wing tips and what I think are the shoulders, although its comb is more yellowish). I realise I'll just have to keep waiting, but I bought three marans from this breeder and the other was a wheaten which is definitely a rooster due to its colours - could they really be 100% wrong on the sexing of all three? (I haven't used them before, so I guess they could indeed be just guessing and hoping no-one comes back to complain...)
Here is a pic of the tops showing how different they look (there are more in the other thread, but I don't want to spam people with my chicks!). Thanks in advance for any advice!
View attachment 1172437