You have Partridge Brahmas, and in another couple weeks, you will be able to sex them based on their coloring (not something you can do with the buff variety). Male plumage looks very different from the female plumage. Once the chest feathers start to come in you will be able to see the differences. Males get solid black feathers, females should have golden feathers with penciling.
For the Delaware chick, males have barring (black and white stripes) through the tail feathers. Females lack the barring through the tail feathers.