a 600 would be fine as long as they don't get outta control in hieght,,or lower branches won't see the light they need,,and produce popcorn bud,,insteada 1/2 quarters
I think cuz on my first grow in one closet of 5 goin male,,4 females,,3 went hermie from pollen from males,,or bad first growing,,could be lotsa things
well,,mine is in an air cooled reflector,,so it is about 6 inches from reflector glass,,and 12 inches from actual light,,I think rule without air cooled reflector is about 18 inches,,or what your plant can handle