Newbie Chicken tender

[ngbells1]

I got 4 pulleys at about 5 weeks. They are now 12-13 weeks and I think one of them might be a rooster. I’m just going by looks and haven’t done a physical exam yet. I’ve attached a couple pictures of 2 of them, the first one is the suspect . Any guesses? I can’t have a rooster where I live.
TIA

 

[Alexandra33]

Solely based on the difference in rate of development, I'd say you have a pair.

 

[ngbells1]

Solely based on the difference in rate of development, I'd say you have a pair.

I’m thinking that they are not all the same age. Then I found this picture online so I think I’ll just see how they develop over the next month or so