Hello!
I am growing 4 plants in one dwc and plants have this brown spot came slowly (2nd and 3rd week photos)
I think I kept lights too close , cfl was like 2 inch away and now led was 12 inch (just raised to 18 inch now).
Or may be nutrients water I used 2/3 of what was on bottl
Solved
Week 3Leaves. Color - Dark-brown