Hey there so where the leaves yellow is usually a great way of telling the problem..being low older leaves if they yellow and eventually die off that's typically nitrogen deficiency ...where as if it were a toxicity it would attack the tips of many leaves. If you up your feeding and the problem continues, then you may want to explore ph, watering or possibly a some of the more minor nutrients like calcium, boron magnesium etc.
We all have struggles like this, don't give up...the majority of the plant appears healthy. ✌️💚🍀