18 or 24 hour lights

400 watt Metal Halide. About 20" away Babies are about 2 1/2 weeks and tallest one is at 4 1/2" the rest of them are maybe pushing 3" and they're getting 24 hrs right now. Someone suggested cutting back light to promote a little stretching. Opinions anyone?

Either or will do fine for your plants. Some people swear by 18/6, others swear by 24/0. I do 24 for my whole veg, just a preference, does it change anything? Research is suggesting 24 for quicker root development and solid future growth, but there is also research against. Either way you go, you will be fine.

if you want a lil stretching just raise the light for a few days.