HELP! First grow, leaves dieing off

[Newtothisstuff]

I hope someone can help. First grow with same problem across multiple strains. Showed up early in veg and continues into early flower. Appears mostly on lower leaves, but has spread across everywhere except top new growth. Affected leaves are faded/bleached, thin but have not fallen off. Water with 6.0ph tap water and nutrients.. Tested run off with pH at 6.0. Is this nute burn, nitrogen def. or potassium. I heard that potassium shows up at flowering, which may rule it out since I've been dealing with this since early on.

setup:
indoor tent
Coco coir, 3 gal. Pots
400w hps (was at 14", just moved to around 24")
using auto flower feed chart from this site (about every other day)
2 fans for circulation
Temps from 67 (lights off) to 79 (lights on)
RH around 40%

[oldjarhead100]

there's lots of thing that could cause them but I cant see with your lights on, take a picture right after the lights go out or just before they go on ,what are you using for a grow medium if its soil try giving them a handful of worm casting

[SoOrbudgal]

You burnt your plants fried them when your light was lower, can't save those leaf now

[Newtothisstuff]

Here's better photos of how it begins. These are autos