The female barred rocks are a bit darker and have less contrast than males. Also, 5 weeks is when you'll usually start to see more color in the comb and wattles in a male. Yours looks female to me.
I agree the barred rock is a female. For the reddish birds, your biggest clue will be if there ends up being red in the wings. Leg size/thickness at a certain age, and of course early comb development can tell the tale too.