10/20/21 (day 1 of 12/12): I flipped the lights to 12/12 last night so today was the first full day of 12/12 lighting. Let the flowering stretch begin! The tallest plants are about 20" tall while the shortest plants are about 13-14" tall. I'm still watering them with veg/grow nutrients for the next week before I switch to flower/bloom nutrients.
Over the past week, I dealt with what I believe is a combination of cal-mag deficiency and also some light burn because I allowed the plants to grow too close to my lights. I raised my lights farther away from the canopy and I dialed down the light intensity a little bit on my dimmer knob. The plants have responded well and the newest growth all looks healthy.
10/24/21 (day 5 of 12/12): The plants are starting to stretch a little bit. The tall ones are 24" now.