Just to clarify, how long have your 6 fems been growing or are you starting all seeds together? If you haven’t started any seeds then I’d go 18/6 or 20/4 and then when the autos show signs of sex you can switch to 12/12 to flip the photos.
You could do gas lantern from seed (12/5.5 + 1/5.5 - on/off) and probably get better results than straight 12/12 but I have nothing backing that except my guess.
For photos 12/12 from start IMO is really only good practice for clones, and even then that’s if you’re just looking to sex quickly during a hunt. Otherwise you’d 18/6 clones to veg a month plus before flipping.