AsNoriuanswered grow question 3 years ago Could be, or maybe not. In my last run one from 17 autos started to flower on week 9 only, sometimes it takes ages, but sometimes it needs small kick, try to give 15 hours of day, don't drop to 12 , if after week no result, most prob it's photoperiods. I had semi autos, some needed 20 hours + of light to keep in veg, one wanted 15 just to start flowering.
You can bring lights back to 18 slowly after if she responds or keep up with 15.
Hope it's not photos, my lateflowering autos were insane by weight, last one - 240 g in soil ;)
Good luck !