When do roosters finish developing?

[Shanda]

I hatched 5 black australorps Thanksgiving weekend, so they are approximately 4 months old now. I know I have a couple of roosters in the mix, but not sure how many. I want to keep the prettiest one and give the rest of the roosters away. I'm wondering when they will finish developing and when I will know which one is the prettiest? I can tell that one has a lot of red on his neck and think he might end up being the prettiest. Also, he is less aggressive than one of the other roosters, so I am leaning toward him. Any thoughts?

 

[Kansaseq]

Black Australorps don't have red on them. Could they be mixes?

 

[Shanda]

They could be mixed...I got the eggs from a woman in Fallon, NV because my banti cochin wanted to sit (I had to make her happy

). She said they were australorps, but they are twice the size of the australorps I already have. Here are some pictures that show the red in his neck - it is much more vibrant in person.