I didn't catch what your set up consisted of. Please post some info on what strain youre growing and under what set up.

At 3 inches youre a ways away from picking anything. Let the plant grow to 10 inches, at least, under 24 hours of light. Minimum of 18 hours of light each day. then when they get 10 inches or above switch the lights to 12 on and 12 off. Make sure the 12 off is COMPLETELY dark.

Every question you asked has been covered on this forum repeatedly. Maybe you could scan through the forums awhile. Just a thought

Hope this helps

Laterz