Sexing 12 week old chickens?

[nszrmch]

I have four chicks at about 12 weeks that I need help sexing! Black and white is Ancona, yellow is Buff Brahma, larger grey is Blue Australorp and smaller grey is Blue Andalusian. Ive read that ancona’s have larger combs but other than that I have no idea as we’ve never had these breeds before. Any insight would be much appreciated

 

[itspebbl]

The only one pictured is a Buff Brahma and the Blue Australorp (which I'm pretty sure is actually a Blue Andalusian pullet)

 

[nszrmch]

The only one pictured is a Buff Brahma and the Blue Australorp (which I'm pretty sure is actually a Blue Andalusian pullet)

Oops! Just added the rest of the pictures. The two grey ones are really similar but one is a lot skinnier and than the other. I struggle a little to tell them apart in photos honestly but one is definitely an australorp

 

[Gray Farms]

All pullets.

 

[drumstick diva]

x2 Gray Farms