Red Sussex cross or Columbian Rock?

[boyswillbeboys]

Crazy question normally, I think, I ordered 5 (got 6) Red Sussex cross chicks straight run, my MIL had 3 of her RIR substituted with 4 Columbian Rocks when they had a bad hatch, I now have 3 cockerels and 3 CR pullets, and I can't tell which one is the CR cockerel, I am new to chickens, this is our first batch, they will be 5 weeks on Thursday. Sorry the last picture is so dark,

 

[five is my dog]

looks like my colombian rock but those breeds are almost idenical.