pullet. compare the feet to the others, they are also a good indicator at this age. Thinner shanks and feet, toes are pullets. The thicker are roos. Whenever I am in doubt with any breed that is the first place I look.
I have BLRW chicks the same age, of both sexes. A couple I can tell, a couple I can't!? Yours looks like the two I'm 99% sure are pullets. It is easier when you have more to compare then to, but STILL not easy all the time! Who would have ever thought sexing a chicken would be SO difficult!