Lower leaves are N defc. for sure,... good eye mate, I was thinking this looks like B defc. too, it fits best,.. but it's rare as hell!
Colderia, it's time to get an in-pot pH reading to see if this is behind the symptoms,...meaning if it's off enough to cause a lockout. I know you're feeding lightly, and they've been hurting some before, so it could still be this acting up,... and B isn't locked up unless the soil is well over 7.0pH, which would trigger Fe and Zn defc. as well,... you had this though, but from lack of feeding I thought, not off-pH,... Only solution is to test that soil, pH and up your Micro dosage for a few rounds (look on the label and see if B is listed there; it should be in this part of the nute's).... As for getting an in-pot pH, unless you have a quality soil pH probe (like the Accurate 8), only alternative is the run-off method, which I dislike because it's a crude method, and a pain to do; here's an improved method for this-(
https://www.autoflower.org/threads/...-for-run-off-testing-and-ph-estimation.41733/ ) .... BUT a very rough snapshot of the pH can be had from a straight run-off collection, in a clean container, using just water.. it will at least indicate if it's grossly too acidic or alkaline in there,... Your pH meter needs to be in good shape too regardless, have you calibrated it recently?