young plants when their growing from seedlings need a nice mix of darkness and light but they seem to grow more in the darkness then they do in the light, ive heard 18-6 and 20-4 but me i was using another type of light and i left it on 24 hours with good air flow and controled temps then i swithed to 12-12 when they looked like this, but if i was you id listen to stinky she has alot of advice