Lower fan leaves turning yellow and necrotizing

Looks like it could be the root system with a mild infection causing the issue. How's the drainage? whats the humidity levels and temps of the tent? try and figure out what caused it? https://www.zamnesia.com/grow-weed/344-identify-fix-cannabis-root-rot in the mean time try some food-grade hydrogen peroxide spray on the leaves, and mix a mild solution for a lite flush with distilled water, then leave for 3hrs then feed as normal. Sort ya PH levels back to netraul

You're having a watering issue most likely and it's messing with your uptake... moisture range is extremely important in organic/living soil growing.

Second photo has even taco, how how is in your room? Any heater next to ? Bottom leaves can die, plant redirects energy and canibalise worthless, shaded and so. N is mobile. Plant is dark, but fresh top grow not too dark, so its light ovefeeding, but far from lockout or toxicity. Those rusty spots is calcium. In soil mostly 3 reasons. A . Excessive N blocks absorption of Ca B. Ph swing, ussually too low C. Led light , they require a bit extra If coco, just not well balanced diet for plant. Light dose of calmag for next feed and triple check ph.

As herbal said lower leaves will die off as they arnt getting as much light as the canopy. It could be a slight imbalance in your PH or cal Mag. It does not look like its effecting her much. Im sure this plant will be fine. I would continue feeding whatever your using and then keep an eye on her. best of luck finishing her up anyway maybe a little flush :) if you need anymore advice just hit my dm up always happy to discuss growing topics :)

there is nothing especially wrong with some of lower and older leaves slowly dying/decaying along flowering, especially with low light penetration bottom of the canopy ....

It must not be organic enough... 😁 A plant can be healthy all the way near the end, so when a plant shows damage it is almost always our fault. not enough info.. plant looks a bit dark, so lockout should be considered. The fact it is paling from inside out is weird, otherwise i'd say it needs N. I'd be patient and see how it progresses unless you have a more obvious diagnosis. heavily shilded leaves can be shed by the plant, too. Senescence is possibly a contributing factror, though is not the sole cause. Could be too much potassium, but, you'd see other symptoms beside the damage to lower leaves here. What symptoms i see are either a bit confusing or in the wrong spots (mobile vs immobile) ... so pH and lockout jump near top of list of possibilities.. use what info you've logged and some deductive reasoning to eliminate possibilities...