Its probably too late to matter as Im sure you know the sex of your chicks. I found this on the Internet:
DORSAL STRIPES AND EYELINES
Chicks with dorsal stripes can be sexed, often with nearly 100% accuracy. The downy coat is similar to that of red junglefowl chicks, so the pattern is sometimes called "wild striping" or "wildtype." There are several things to look for to determine the chick's sex. A pullet will have refined,well defined markings while the cockeral's coloring will be more fuzzy and blurry. You can start with the dorsal stripes (stripes along the back). A male's stripes will be lighter, less well defined, and fade out before reaching the head. A female's dorsal stripes will be darker, often defined with a outline, and will extend much further onto the head. Check the head for two clues. If the chick has a long, dark eyeline extending towards the ear, the chick is almost certainly a female. A male may have an eyeline, but it will be short, light and blurry. In addition, look at a triangle on the top of the head. The triangle on a female will be dark, have a sharp contrast, and may be outlined by an almost black outline. A male's triangle will be lighter and a bit indistinct.
Can you share your results so we can see how well this information matches what you found in your group of chicks?