Hm, mayor Dominiques. I'm not an expert on leg color... If you google those breeds as chicks I'd say they're not jersey Giants. How old are they? My cuckoos and barred started the barring at 3 weeks ish.
Maybe you got lucky and got some black copper marans! Where did you get them? Maybe so,done else can shed some light on the barring, I just know my cuckoo is 5 weeks and she's been barred liked that for weeks!