Unless you live in Northern Alaska or some place, your not getting 18hrs of daylight. Go check your local Sunrise - Sunset times. I'll bet your getting about 14 to 15 hrs.
Here today in NorCal, Sunrise is 5:42am - Sunset is 8:24pm, that's about 14 1/2 hrs.
Today in Fairbanks Alaska: Sunrise 3:29am - Sunset 12:11am, that's about 20 hrs!
Put some lights on your plants for a couple of hrs a day,and they will re-veg. My light comes on at 3:30am till 6:00am.
Good luck
Peace
doublejj