My guess would be 2 roos and 2 hens, based on the red combs and waddles on two of the chicks and the lack there of on the other two. There's a better place to post though for more expert help:
First 3 pics.... Looks like the same bird, but not sure.... Looks like definite cockerel to me... That's a very red comb and pretty good size for 4 weeks... Just my opinion... The black austrolourps (I believe is the breed I can't tell well enough yet)