I just switched to 12/12 yesterday. Only got about 6 hours of HPS in yesterday & just about the whole 12 today (Minus about 2 hrs today when I blew a fuse). I was running 18/6 with 265w LED for veg. I've got the temp & humidity good. From the 1000w HPS bulb to top of plants is just about 24". I just raised it 2" when I checked with a measuring tape. Some of the leaves seem to be turning partly yellow. Could this be light burn? I've got 7 WW going. It seems way too soon especially since the light wasn't too close. It's a closed hood. Should I be measuring from the bottom of the hood or the actual bulb? And if not light burn, ne idea what it could be. The plants have looked good & healthy during the entire veg. Also the PH is always rt on pt. I'm still learning as I go. Any & all help & advice is greatly appreciated.