First Grow, Bubblelicious.

[Italiano715]

E-Indoor
E-Soil
E-I'm using a soil mix 2 parts Earthgro Organic Humus and Manure .05-.05.-05 1 part Promix ultra organic sea based compost with AVEC, and 1 part Perlite.
SCLR - 6.6
E- Tap
E - source PH 6.7
E-Flower 37 Days
E-Fox Farms Tiger Bloom
E-1 tsp per gallon every 3 days.
E-400w HPS about 6 inches away
E-I run the lights at night. Temps are between 70 and 80 degrees.
E-50-63 % RH
E-Lighting schedule - 12h on 12h off
E-Type of ventilation your growbox has - 100 CFM inline can fan for exhaust, Passive intake.

Do you ever flush in between waterings? If not, that may be your problem. You don't want to give nutes every time you go to water. You only want to give them nutes every other watering. If you do it every time you will build up the salts in the soil which can lead to lockout as well as a nute problem. Try giving them a nice flush the next watering with just Ph corrected water and see if that helps any. Remember you won't be able to change the look of the already damaged leaves, but it should subside and the new growth should look fine.