are you counting dawn and dusk times regarding sunlight spectrum hitting the plants because plants are very aware of this.
& the solstice date is important. are you following natural sun cycle regarding times beforehand ? you should have lined up times from day one with dawn / dusk times regarding artificial lighting. the stress from exiting totally artificial lighting is always an issue. they should be getting sunlight from the time you get clones if your moving them outdoors. i only run seeds but ya, they get daylight from day one ...... hardening off is a fools gold recipe for those stressing plants from the start. they should never get artificial light unless its inside greenhouse ( already getting natural light ) from day one -
outdoor, plants will start a very sloooow walk toward flowering after solstice, you will not see it outwardly until august but the process has started long before. look toward the natural process of an annual plant outdoor and mimic nature as closely in all aspects and then you will deal with less stress upon the plants. we get 14 hours 20 minutes of daylight on august 1st, w/ dawn dusk / twilight you add an extra hour. so indeed, plants will flower with 15 hours plus of light but the key is solstice and the time crashing 2 minutes per day and by me the temps dropping also quicken the process.
