What kind of soil? What were you feeding before the last week? More info needed.
More reading for you.
https://www.rollitup.org/t/yellowing-lower-leaves.956738/
https://www.rollitup.org/t/what-causes-bottom-leaves-to-yellow-and-shrivel-up.956834/#post-14007312
https://www.rollitup.org/t/yellowing-2-wks-after-start-of-feeding.956732/page-3
Looks like a few things to me i dont think your lacking in nitrogen
But im a hydro guy so i cant say
and if they are still in the pots in the pic, I believe they need to be up potted, so possible root bound?
Not sure what lights you are under, could be the light is too close, indicate by the yellowing from the tips in, and the slight clawing
Could be the start of a calmag issue but it's not really bad or positively identifiable to me. Maybe someone else can help us out .
Stop the fluctuating with the ph, ph your water to 6.2 to 6.5.p every watering , instead of the swing
Feed at 25 percent and raise until you feel suitable , just go with your 3 basic nutes for now
The ffof should have plenty nutes in it for now without needing to feed, stick to the KISS method, instead of all the amendments right now