Early veg stage and leaves are shriveling and turning brittle please help!! :((

So I have it in a 2 gallon pot with drainage holes and I am using a 400w HPS lamp which is like 12 inch away and 2 fans it stays about 75-80 in my closet and I have used nothing but 5.5 ph adjusted water..I WAS over watering but I let it dry out for 4 days then put it in a new pot with new soil and watered it A LITTLE and then went to sleep and when I woke up my leaves looked like this!! ( <<<< this is like the day before yesterday.

The leaves are also brittle as fuck and yellow/light green

It looks fine to me, a little bit of yellowing at the tips isn't terrible.
Those pics you JUST posted, however, are definitely a N and Zinc def. *edit*
Have you started feeding them yet? How big are they, and how old?
FF Grow Big has traces, and you should have them on something high in N anyways if they are vegging.
I'd just pick up that and start feeding 1/2 strength. They look good, besides. Well the first pic did, at least.

It is not on all of the leaves tho mostly the lower ones

This is my 2nd biggest one it is also starting with brown spot that turn into light green/yellow areas

I'm scared to feed them.. What's the difference between food and nutes, what should I get if its needing zinc and N?

Did you not see the pics?