Well, I am pretty sure you can leave the polish out of the parent possibilities--you would see crests. Any bird with yellow skin (or carrying a hidden copy of the gene) and dark legs could be one of the parents. If Buffs Orpingtons are the only buff birds, then I think that is possible, although leg colour is an issue. Do you know whether she hatched from a standard or bantam egg? I don't think mama had to be a japanese, but one of her parents certainly is.