one in flower one in veg(i think)

hypothetically speaking, there are 2 plants, one trainwreck and one haze mist. now the trainwreck is well into flowering but the haze mist is just getting fucking taller. i have been growing them in soil under a 400 watt hps light on 12/12 since i got them as clones.(i know it shoulda been 18 hrs to 24) but either way one of the plants is still getting huge. can i put it outside to allow the flowering plant to soak up all the light from the 400 watt then bring the other one in once its finished or does this stress the plant too much?

i dont see any reason why you couldnt do that. id throw her outside, and forget about it untill you harvest the one under the light. she'll thank you for all the extra lumens anyway. lol