I not sure what this is. It’s only on the one plant. I feed it mega crop 3.5 grams per gallon. The last feeding was Friday night. I PH the to about 6.5-6.8ish. Light is at about 19-20 inches for the top. The white stuff is drywall dust that fell I wipe it all off

Your plant looks pretty good. Do you know the pH and PPM of the runoff?
I don’t. Usually when I water the PH is around 6.5-6.8. I was going to do a flush and check the everything tonight when I get off work. What should I be looking for?
@Joe_grow937 I am for 6.0-7.0 pH when growing in soil. 6.5 being the sweet spot. For PPM in the medium, it depends on how old your plant it. Late Veg I like 450-700PPM (500 scale)
My PPM was super high. when I did a flush and checked the run off it was like 4000. After I was done with the flush it was like 575. The PH was 6.8.