if they are truely needing that "much" extra time then id ASSume you are stunting/slowing them down somehow , and if the late nanners arent due to the prolonging growing/flowering then id look into my environment and methods
but honestly i believe if the strains are stable you are pushing them for too long , but hey , maybe they arent stable , unfortunately big comercial breeders tend to not care like the little guys do
peace :Cool: