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I never considered it to be a "normal" thing . The packaging said 9 to 10 weeks and from researching i found that most afs start to flower in 3rd to 4th week and i saw a video of this strain finish in 75 days so i assumed human error on my part. Well with that kind of wait time a photo could be quicker :/ The reason i chose it for first crop was thinking it would be done in 10 weeks. You live you learn as usual .7 weeks to start flower is unusual, but it does happen.
Most of mine flower during the 5-6th weeks, and ripening usually takes 7-9 more weeks.
My record is 10 weeks to start flower.
It's probably coincidence that they started flower when you switched lights to 18-6.
Autos can get huge in hydro, and yield huge, and the longer they veg, the bigger they get.