looks like you are in soil. your nutrient pH should be 6.3 in soil. you mix your nutes and then adjust the pH. that light is way too far away. what size is it? 2' for a 1000w. 18" for a 600w. if the plants are just going under HID lighting then keep it 12" further away and move it down slowly over the course of a week.
what is the ppm of your nutrient solution? how old are your plants since they were rooted. lockout is a MAJOR issue at a pH of 5.4 in soil.