G'day, and welcome to BYC! Glad you decided to join our flock. Isa Brown is one of a number of labels under which some hatcheries market their Red Sex Links (a particularly common label for ASLs in Australia), which are produced by crossing a red gene rooster with a silver gene hen. Not only can the offspring be sexed by color at hatching, but they are egg laying machines, outlaying either parent breed. It's one of the interesting quirks of hybridization. You should get loads of eggs from those three ladies. Please feel free to ask any questions you may have. We are here to help in any way we can. Cheers.