Do you know if they are all the same variety? If so, I do think the others are hens based on their wattles and combs, both of which are much smaller than the rooster's. From these photos, the tail feathers also look more hen-ish to me. Orpingtons are often fluffy, but I have had one or two be leaner, especially while still on the younger side, but hopefully someone with more experience in identification will come along and answer.