Yellowing leaves

The older the plant, th emore you learn about your methods of growing it... Lots of ways work well for a few weeks. Only well-balanced fertilization will be consistent long-term, Plant's aren't pickier in flower so much as the plant is 1-2 months old and showing the flaws of fertilization choices that have slowly built up over time and gotten out of balance in a way that causes symptoms... Are they a little pickier? Sure, but for most plants, they can stay very healthy looking up until the end. Some senescence is unavoidable but it's going to vary per seed. So, if they get ugly, that's user-error and shouldn't be blamed on outside sources. If the pH is 6.5, That will not lockout anything. That's a good pH for soil, because it helps make N more available. In soil the source of N in fertiizers tend to need microbes to break it down before it can enter the plant. Depends on the fertilizer you use, though. Not all sources of N have the same steps to be plant ready. if you buy soilless nutes, they are plant ready the moment they dissolve. you can use these in soil, but might as well go soilless if you do go that route. You plant is just barely old enough to show symptoms of mg deficiency. It takes 5 weeks from onset of mg-deficiency problem for a symptom to be visible. It's possible but this looks more like nutrient competition. Better to get that in check before playing mad scientist adding this or that to it. that alone might clear up the issue or you may also need a little more of something.. there are several moving factors and they interelate -- see mulder's chart to get the gist of complexity at play. Your plant looks overly lush. there's no info on fertilization plus the unknowns of what came in your soil. I'd dial back a bit rather than giving more. a foliar feed can be useful for an on demand treatment, but it's not something that you want to do persistently in the long-term. you want to get your fertilization balanced. The roots should handle nutrient intake for the plant with no reason not to do it that way. Potentially clogging up stomata with repeated foliar sprays or the disease vector it creates is not worth it to do persistently throughout. you might be low on something but overall your plant looks overfed. Try to re-balance it and take notes.. what works repeat.. what doesn't work try soemthing new next time. when you have a more refined formula, it takes weeks even more than a month before you see any nutes can buildup or be depleted relative to rate of use in the plant. You definitely need notes at this point of refining your fertilization methods. Any new soil product will require some adjustment too.