Funny you should say that as i have just raised my hps to 18" to get them to stretch a little over the next 2 weeks before i set them to flower.
I think your already in flower though so its up to you.
When i am flowering i keep the lights as close as possible
10 in one 12/12.under 400hps.
8 in vegg under 250hps and 8 babys under flos.
i think i need another lite, my other 400hps, blew a hole in itself for some reason, mite get a 600, just for now.
i really want 2 1000 hps, just for flower, then i could use all the lites i have for vegg or mothers/clones ect...
its all good, ive only been growing 9 months,so i can only expand.
i take everything too far.
well all have plenty bud by spring, i never grow enuf.
i dont relise how much i smoke.
£300 every 4 weeks, min.
so im trying to grow myself a plant a week. 1 to 2 oz, will do just fine, and everything else i grow too or over, is also good.