Can you Grow Autoflowers on 18 / 6 Metal Halide throughout?

Hi, so i have 2 grow areas, 1 with a 600w metal halide perm. on 18 / 6 and one with 2 x 600w HPS perm. on 12/12 as i usually grow regular photoperiod plants.

However i have a couple of autoflower seeds which i was going to plant, and i was just wandering would they grow best left in the 18/6 MH tent throughout, or in the 12/12 HPS, or what is the best way to do this?

Many thanks.

I'm pretty sure most people do autos on 20/4, or 18/6 depending on your needs. And i'm sure your MH will be fine, but why not take this opportunity to get a dual spectrum?