The #6 cylinder (driver rear) is often the first one to go bad, presumably due to poor cooling (the reason why we dremel out the cooling passages during rebuild) and possibly also due to leaner fuel supply. This does not account for #3 (psgr middle) being almost as low.
You should have a leakdown test done to ascertain the cause of your low compression: ring seal vs. valve train issue before making a definitive decision about needing to rebuild.