If the plant is already flowering.. why would you want to put it back into veg? Are you wanting to take cuttings or something? I just dont understand why you would want to flip them back? As mentioned by Startingreen.. if you put the plants back on an 18/6 cycle.. they will force back into veg after a few weeks.. this stresses the shit out of the plant and will often result in hermaphordite plants (SEED WEED!) My best suggestion if you need to move them indoors.. just keep them on a 12/12 cycle and let them flower out.. your plants will thank you with dankness in the end Good Luck!