I agree with pcragz,
last thing you want is that green algae gunk building up on your roots, what do you intend to transplant them into or are you keeping then on the flood table, if so i would cover the table with some light proof sheeting and cut out squares for the rock wool or completely cover with clay pebble's or gravel
Have they showed any pre flowers yet i had 5 Medicine man show pre flowers after 4 weeks veg saved me the hassle of finding the males when i switched to 12/12
Keep us posted