Leaves drying up and dying need help

My indoor grow room is in about 64 degree temperature, and I'm unsure of the humidity. I'm around week 4ish. It is in DWC ppm level is about 312, and the ph is around 6.15. I'm using general hydroponics. This is under a 450 watt vioarspectra led. I thought at first maybe light burn, so I moved it from 12 in away to about 18 in away.

Hi Beavercat,
Not a dwc grower but it seems that the nute level is a little low. Also to me it looks a bit like a Mg deficiency. Use epsom salts unless you think you may need more Ca...in which case use calmag instead. Using tap? Hard or soft? I always add some extra mg.
JD

Thank you for the input. I was holding off from putting more notes into as it's easier to add than to take away. I wanted some other folks' opinions first before I altered anything. Its spring water with a ppm level of about 10 before nutes.