The light cycle needs to be consistent, otherwise the plant will grow very slowly, and won't fill out, due to it trying to flower and veg and flower again. You'll just get ugly fluffy buds. Stick to the 12/12 for flower. It's best to stick to what's in nature, cause nature's been doin' it a long time.
edit: Going back and reading your first post, I would maybe try to re-veg the lemon haze and let all your plants veg for a while longer. If you just topped them, they'll need a bit of time to recuperate. Let them veg for a while longer and then flower them all at the same time. That way you don't need to separate grow rooms.