I would agree spark to some degree. I got my BG from a decent fish farm but nothing said they were of any GREAT DNA chain. I have done nothing but put air in my pond, supplement feed, and cover and I have 11 in BG so like you said I think I am missing that one extra "thing" or tweak, if you will to get to 12 inch 2 pound BG. Or maybe I have a few just haven't caught them yet? I don't know for sure. I imagine at the 12 inch 2 pound mark they can get somewhat hook shy and smarter than your average gill....
RC