rooster or hen ?

[familychooks]

Hi, I am in Australia and have raised 5 chicks who are now 14/5 weeks old.. Someone is Crowing in the morning and I can't work out which one(s) are roosters?
Two have very small combs, but as they are different breeds it is hard to compare
The three in question are:
Rhode Island Red


New Hampshire - Palomino

Blue Australorp


Any help would be appreciated
Thanks