SOil grow Week 5 goin on 6

HEy guys I got my grow going well and my first baby is doing well transplanted into a 5 gal pot with new soil no nutes yet just good old water and light and CO2. But Im running into a dilemma here in about a week im switching the big girl to her 18/6 light schedule but all my plants are in the same space and i was wondering who had some idea on how split the space and keep it light seal any suggestions will be helpful thank you again