This could be an old problem,that hasnt run full circle....lets try some light nute's tho.
mix up some water with nute's then set ph at 6.8 like normal.Changes can take a week or more to show improvement,we need to make small change's one at a time till we nail it down. No foliar feeding (spraying),it kinda looks heat burned.I'll check the other thread that has the better pic's also.