So @chooks4life the BA normally grows in faster than the others in terms of legs/feathering/comb/etc? She's like a weed! Won't stop growing!
Well, it varies, but in this case I'm referring to hatchery types. High quality RIRs and BAs are nothing like what you get from a hatchery on average. Some hatcheries produce pretty decent stock but generally there's no comparing the product of a real enthusiast with a commercial hatchery which churns out chicks like there's no tomorrow.
There are often very significant differences in hatchery breeds as compared to the expert breeders' versions of those breeds. Sometimes they don't even look like the same breed.
Purebred, high quality BAs are more compact but still large, and purebred heritage type RIRs are chunky, large birds as well; but hatchery bred types are generally, in the case of BAs, lanky and large-ish birds, who often do look sort of stretched out as chicks, and the RIRs are generally more tight bodied, slim birds, really they're almost of the same overall type as a Leghorn or Isabrown when you get them from a hatchery.
Yours appear to be a normal hatchery offering, so to speak. I don't know if the BAs develop gender characteristics quicker or feather quicker overall, mine didn't seem to, just that they tend to develop more length, width and depth to their skeletons quicker than many other breeds, at least when young. The hatchery type RIR tends to show gender development quicker than the BA.
Best wishes with them.