Cyrptonic I am not trying to judge your knowledge of growing but I thought autoflowering strains weren't photoperiod depevendent, I have read that if you do 12/12 on autoflowering strains that it will effect your yield, but negatively, I heard keep it 18/6 all the way through harvest.
No worries man, I dont that much lol. And yes, your right, AF are not photoperiod sensitive, if they have been bred correctly. But, the Nirvana AF NL most ofter do not flower w/out putting them in 12/12. My plants were vegged for seven weeks or so, and would not flower until I put them in 12/12.
So, when you switch to 12/12 they did start to flower right? When you switched back to 18/6 did they slow down or stop flowering all together. Judging by your pics, it looks to me like your plant reveged. Your bud sites should be more developed right now.
Not sure what to tell you. You can leave it 18/6 to see if they will AF, but they may not. Or you can switch back 12/12 and see what happens. Never switch a plant from flower back to veg times, it can really screw the plant up.