Just like Doobsday said:
You need more lights than that to flower one plant. you'll get leaves, but you need lumens (more watts) or you will get a few fluffy popcorn size buds that shrink to nothing.
What would help if your 18? Anyways they are stretching you should get a 4 foot shop light for these and start them with that get it touching the top of the plants its fine .