Please help first time grower

Hello! I am a first time grower, I have tried to do my own research but I can’t seem to figure this out, I have 4 autos for my first grow, 5 gal pots in coco coir70/30 perlite, using cronk Bonnie and Clyde also Calmag mixing both at the recommended 2ml per gallon, last feeding was Thursday, soil is still moist, ph going in is 5.8 ro has been 6.4, 1048ppm these plants are 4 weeks day 25, at first I thought it was nutrient burn, then I got a light meter and the light I’m using is a 400 watt VIVOSUN which says it should be 24” at 80%, 1200ppfd I feel like that seems like led burn, but I’m at a height of 30”. Any help would be much appreciated, i really want to do right by these girls!