Yellow leaves

Hey there if you look at the leaves they are all sagging ot looks like your starting flowering in these photos I'm sure it has todo with watering If not watering then you gave to much nutrients

Some bottom leaves without proper light or air movement can be canibalised/ energy redirected by plant, thats normal. Here i would bet more on wrong watering regime, aka underwater, soil build up, lockout or toxicity from this. Reduce nitrogen feed part for a bit, rethink how much and how often you water .