m0useanswered grow question 2y ago You could try and increase the dark period, but it won't do a whole lot. The dark period could maybe help it build up flowering hormones but it does not really need more as its already in bloom. You might just be stuck waiting for it to finish. sativas take their sweet time.
Aslo keep an eye on your trichomes as they should be the main indactor of when the plant is ready to harvest.
Clear trichomes not ready, milky trichomes good to go, amber trichomes overripe. A mix of them also good to go.
Good Luck!