could anyone guess an age for my chicks?

[brooklynrose]

I picked up 4 black new jersey giants a week ago and they didnt know the age of them :/ could anyone take a good guess? this is my first year owning chicks. I have 4 black nj giants, 1 easter egger,4 rhr,and 1 white leg horn.

 

[nchls school]

3-4 weeks