GMSgrowsanswered grow question 4 years ago Can stretch anywhere from 1/2 to 3 times it size in 2 to 3 weeks of the stretch. Wont hurt that you just topped to switch to 12/12. It's how high a space do you have to keep the lights the proper distance from the plant. Once you start getting to close your girls buds wont grow to their potential. Switch when ready. Cheers