Just thought I'd share my own experience with racking my brain over leaf spot diagnoses: after spending crazy amounts of time obsessing over nutrients, temperature, water sources, etc...across several grows, I realized that nutrients were always, without exception, the last thing I worried about. Instead I started disregarding my leaf discoloration and continually monitored my roots instead - what I found out was that each of my plants had unique ph desires (not huge fluctuations, but enough to make me more observant of root lock, and less of the nutrient levels). I realize I'm rambling, but in short, try not to over analyze the leaf too much, as a lot of things can manifest in similar ways, but rest assured if your roots are reacting well, so will your leaf appearance. Good luck!