This was my guess. The black ones came from a live poultry market where they would have been dinner very soon, they almost died when I first brought them home. Thanks to some great advice here I nursed them back to health and they are unrecognizable now compared to before. They free range all day, and love cracked corn, raisins and cherries as snacks. They are also great at keeping the bugs down.
The darker orange girl is Miss Independent, I posted about her funny behaviour earlier today. These are my first chickens and I'm in LOVE, lol.