I have found that in flocks with multiple breeds, individuals of the same breed do tend to hang out together. It was a bit unexpected, but I've had it happen with 3 separate flocks. In one flock I had several birds each of three different breeds, plus one single bird of a fourth breed. The single bird kept going from group to group, looking for a place to fit in. Just another way that chicken flocks mirror the social structure in high school -- nothing but cliques and full of bullies!!
Seventy eight chicks!!! Wow, you've got your hands full.