HenThymes is correct. Do any of them have white shanks? Have known of some breeders crossing Buff Orpington Bantams with Buff Wyandotte Bantams for fertility in their Wy. These do seem to have a Wyandotte look to them. They are very pretty, but difficult to tell quality in a photo. I would suggest taking them to a show and allowing a judge to critique them. Ask the judge or a good breeder of Rock bantams to look them over after the show.
Talk to the seller. They really need to know these are NOT Orpingtons. My first trio of Buff Orpington Bantams came with a pair of Buff Rocks. They were a hatchery assortment. I was 18 and took them all ands old the Rocks. Then I acquired some eggs from Brazelton to improve what I had. If you have patience, you could acquire a good White Orpington male and outcross to these hens. Then take those pullets back to the sire. May take 2 or 3 generations, but it is possible. Just cull heavy per the Standard.