Veg to flowers transition phase

your plants is fully pre-flowering. You will see the flowers (pistils) in a about 7 to 12 days

you can see preflowers before. These are the single calyx at base of any axilla (branch). If you leave them in vege long enough, you'll see them without flip. early flowering at normal bud sites are not "preflowers". So, you should see those preflowers within 7 days, and you should see pistils at terminal buds, possibly elsewhere, shortly after that (10-14 days). YMMV, as genetics can cause some variety here. But, if the plant isn't stressed/delayed, should not take long. By 21 days post flip, should have some early formation of buds at every growth node with a growth tip if it wasn't lolipopped. Light is proportional to hours of operation. So if you went from 18h to 12h you need 150% more power from same hanging distance. 66% becomes 100%, if you did it right. Hanging distance should be about coverage. Last-ditch resort for adjusting how many photons per day (DLI) are applied to the canopy - averaged across entirety. So if you were greater than 66% in vege with current hanging distance, you'll need to get the light a bit closer to maintain same DLI as in vege -- assuming it was growing really well in vege, and you want to match that. REad up on daily light integral. Clears up a lot of the misunderstanding about light. Think of it as a particle in this case. 1000 photons of light over 12 hours gives teh same growth potential as 1000 photons over 18 hours. the difference is the rate at which they are applied, but the plant can only process X amount of photons per 25 hour period. This ceiling depends on climate and ambient CO2, so it varies per garden. In general you want to shoot for 35-40 DLI and then observe and react to the plant. In future, go with what you learned from that trial and error. take notes. if growing photoperiods, always work backward from needs of 12/12. This ensures your hanging distance and 100% power is properly scaled to need. In vege and 18/6, simply turn dimmer to 66-70% power at same hanging distance. Again, distance is more about geometry of light coverage... some excceptions due to exteme contexts, of course. e.g. maybe, you don't have a dimmer... then you need to play around with hanging distance and maybe use fewer hours of light in vege without causing flower. hours of light are directly proportional to dli. 10% fewer hours equals 10% less DLI, all other factors the same.

Generally you'll see a transition at around 2 weeks. I'd just leave your light at it's veg height and start drawing it closer as flower starts and progresses.