Your first batch of chicks will drive you nuts.
This one is bigger than the other of the same breed, tail isn't filling out as fast. Boy? Girl?
All 12 of my 2012's were girls but I sweated every difference (2 each of 6 breeds), every "is that comb a LITTLE red?" "Is that one feathering faster than this one?"
I did better in 2015 knowing they are different even when the same breed. Trouble the 2017 Barnevelder 'oops' cockerel was SO obvious at 3 weeks. No need to sweat the boy/girl thing , it was a done deal.
This one is bigger than the other of the same breed, tail isn't filling out as fast. Boy? Girl?

All 12 of my 2012's were girls but I sweated every difference (2 each of 6 breeds), every "is that comb a LITTLE red?" "Is that one feathering faster than this one?"
I did better in 2015 knowing they are different even when the same breed. Trouble the 2017 Barnevelder 'oops' cockerel was SO obvious at 3 weeks. No need to sweat the boy/girl thing , it was a done deal.