BO, RIR Roo or Hen?

[4sillymonkies]

I purchased this lot of three from a local feed store on April 1st. They were approximately 1 week old at purchase putting them at approx. 7 weeks now. I'm fairly certain that the RIR is a cockerel, but I'm concerned that both of the BO's are also cockerels. Can anyone help me identify. Please be specific when explaining how you know I'm new at this and want to learn not just be told. Thanks for your help!

 

[cluckmecoop7]

Those both look like cockerels to me.

 

[Rhodebar Lover]

They both look like cockerels due to comb size and redness.