Welcome to AFN, I'd advise doing a lot of reading!
Get the propagator out of the 12/12 closet with a 600W light, that's insane. I germinate with 1 13w CFL 3 feet off the top of the container. Does your propagator have a built in method to heat itself? Transition the plants and bring the lights in closer as they grow more leaves, but for germination you need no real light just warmth, once the seed breaks the soil / medium, just a little light until you have more leaves than cotyledons, then move the light according to plant response.
Autoflowers thrive in 18/6 and 20/4 as they have no defined phase, while you can tell when the plant is vegetative and bloom, they do these things by themselves. So more light will give your plant more time to perform photosynthesis (GROW!).
Again, do NOT put the propagator in there with the 600W light, in my EXPERIENCE, this will kill or stunt your seedlings. Ask my 60DW's that stayed with cotyledons and one leaf set for almost 2 weeks.