Leave the lights on 18/6 until flowering then use 12/12 when you want to flower. As long as the plants just started flowering you can still re veg them
he has autoflower plants..dont change the light at all!!!!! keep it as is some autoflowers dont get very high..they are designed to be small remember that when a plant starts to flower she will have a growth spurt so she will probably double in size before she begins to put on weight in buds
You probably have auto flowers.. don't try to switch them back to veg...just go with it,flower and finish those out, and start new seeds for a new cycle asap.. Remember, the bigger the pot you plant in,the larger your plants will grow. If your in a red solo cup or a 1gallon pot your plants will only grow 8-12inches because there's no room for the roots to grow...even if there flowering and your in a tiny pot I would transplant them to a bigger pot...they shouldn't get too bad of shock and I think the end yield will be worth it
also, your plant might not be getting enough light to grow bigger..in flowering the plant needs more light to produce more.. cfls are hard..cuz in flower you need to add more