When you switch to flowering you might not have kept a close eye on the temp of the bulb and the distance between the bulb and the top of the plant.
I have trouble sometimes getting it right, the first couple days I'm constantly monitoring the temp in relationship to the height. Adjust and readjusting. Do you not check on em at least once a day?
Personally, when ever I switch the atmosphere they are in or re-pot, adjust ph levels, amount of food given I keep extra close attention on them to make sure any errors can be corrected in time.