Lights

My girls have been under 1000k mh for there whole life, about 6 weeks. they are growing to big for just the one light so i want to move it to two 1000k.

my problem is that i only have 2 hps lights.

if i put the girls under the hps for 18 hrs will they stay veg? or start to flower b.c of the color change?

No, they'll be fine. Flowering is determined by photoperiod, not spectrum. There are slight differences in the way they grow under HPS because of the red:far red ratio of light but as long as they're not getting more than 6 hours of darkness you're looking good.