Transitioning to flowering has some complexity in it for me. I try to time the transition to flowering to be a week after the transplant to the final pot. I can then load the final pot media with Bloom nutrients, and the plant will have a week to get used to their final pot before I switch the lights to 12/12. I give them a good water that day before the transplant; transplant; then water the new pot around the outside for the first few waterings/feedings. I also give the tent a good ol' cleanout as dust, etc, is ok in veg, but in flower I don't want dust floating around my tent sticking on my buds, this goes for the fans, lights, etc. A H202 clean of the inside tent surfaces also happens to kills bug eggs, etc. that may have got in. I also lower temperatures by 5c when transitioning to flower, to mimic Autumn coming. Good Luck!