Nutrient burn? Salt build up? Over watering?

Ok first Time grower, plaants in end of first week of flower, soil medium is canna brand cocoa, nutrients: canna A&B, rhizotonic, cannazym, cannaboost, water is ro, ive been keeping the ph of my nutrient solution at 5.5-6.0. I have 4 1000watt hps lights, room is about 17"x8" , co2 is set at about 1500 ppm, there are 3 oscillating fans along with the AC blowing, carbon filter, plants are in 3 gallon pots and are a couple feet from the lights (just perfect for my room). NOW FOR THE PROBLEM. I have two strains darth Vader og kush and LSD, each strain is experiencing nearly the same problems both indica dominant.

Darth Vader: slight discoloration, some leafs really light some are dark green, upward/inward curing, slightly purple veins.

LSD: discoloration of leafs, internal browning on leafs, upward inward curling, small thin new growth slightly purple veins.

I think the problem is either a salt build up or over watering, I'm thinking about flushing with 1/4 strength nutrients

I do not know how to post pictures from the iPad maybe somebody can also help with that. Cheers!