are you changing the type of light? say from hps to led.... if that is the case I would wait maybe 7 days for them to acclimatize to the new light source. If not they are ready to flower when you are.
You can increase their light to whatever you like honestly they should take right too it.. Or if you wanted to start your flower throw them in on a 12/12 straight away. They look ready! Happy growing! 👊