I strongly recommend regardless of what your growing once you start cutting back light hours you should never add back on cause either photo or auto genes that could cause it to stress and hermie on you; I strongly suggest keeping it on 12/12 and for that matter once an auto reaches the point of preflowers throwing it into 12/12 has cause little yield difference in my experiences.... I run autos in the 12/12 flowering tent all the time, while your on 12/12 if you got any photo beans lying around don't let the tent go to waste throw some photos from 12/12 and by the the time the nirvana sky finishes you could be almost done with some super dank photo strain in that amount of time.... Ride it out brother, if the bud isn't of good quality it can always go to making concentrates.... Good luck with the rest of your grow and btw @MedicGrower 
