I keep it at 20 inches or so and let them grow into it. I am at 10 inches from the light in the 6th week. I think with a LED light anything over 600 Watts at 12 inches in veg or early flower will cause the humidity to be low in patches causing the taco leaves. Also, I read somewhere, having the light too close like at 12 inches or closer...requires CO2. It's hard to pinpoint exact reason for issues.