I agree. Even the others are really big, so I'm thinking they're older than 6-7 weeks by at least a few weeks :)
white leghorn? Roo or not? - Page 2
Lohmann browns are a sexlink breed. Pullets feather in mostly red with some white. Cockerels feather in white and will develop red leakage as they mature.
No matter how old a flock is, there is always going to be a leader. It does not mean that that chick is male. The Lohmann chicks can be sexed by color, but your just going to have to wait a few more weeks to make a determination about the Australorp.
You can see one of my Australorps in the back standing tall, with her necked stretched. My only rooster is that red Easter Egger.