The 8 month old, definitely a girl, as for the 2 month olds I can't tell by those pictures, of possible could you get full body shots of them standing up (so I can see posture) and a picture of their combs
I would say that the two younger ones are still too young to tell really. Like @Tofu the chicken said if you could get some more photos you might be able to tell but I am not sure. The 8 month old one is a hen for sure.
They probably are too young to say, but my guess (which due to the age is barely better than just guessing so not accurate) the lighter one might be a cockerel and the darker one a pullet but you should post pictures when they are older