I bought 8 chickens day old from a well known breeder here in Australia. Ended up with 11 as they send extras just in case and 1 has since died. So I now have 3 RIR, 2 cross whites, 3 cross blacks and 2 cross browns. Anyway of the 3 reds 2 look like mini adult chickens along with all the others. fully feathered, tails etc. their is one RIR however that has really short tail feathers and is way behind the others. Probably about the same size but just seems slower to develop feathers. It also seems a bit more stout with bigger legs. Do roosters grow slower? They are now 8 weeks old. I'll try to get photos.