switching light cycle

ok so i have a mrs. in a box with a 400w HPS in my basement and right now the 12/12 goes like this 9:30 am on 9:30 pm off im getting some bad temperature readings as it hits 55 at night and 85 during the day and i want to switch it up so the light is on at night to keep the temps. up during the cold nights were i'm at. so my question is does anyone know if i van switch up my light cycles with no ill effects on my lady and does anyone have any experience with doing this? thank you very much MVG

i would say to change it slowly by only like an hour or so everyday, then i think the plants wouldnt even notice

good question. i just did that myself for the very same reason. I just let the dark period extend by 12 hours (so they were in the dark for 24 hours total) and then just went right back into 12/12.

They are only a week into flowering so i can't tell you if there will be any ill effects. They look great though.

any other thoughts??