Hey I have the same size tent, the same light, and I have grown gorilla glue!
Light starts on a 24/0 cycle (18/6 is fine too). About 30 inches away at 100% strength. You could get away with going 40%, but without a PAR meter, it's hard to tell if you're giving them the right amount of ppfd.
With 6 plants, just pay attention to the four corners, if they look like they are stretching with thin, weaker stems the drop the light a few inches. It's gonna be a tight flowing phase for you, so I suggest flipping kind of early. Maybe after 3 weeks after they pop.
Good luck and enjoy!