Leaves going yellow during flowering is perfectly OK and somewhat normal. Do not cut them off unless they are completely yellow. Cannabis being the smart plant that she is, "recycles/re-uses/re-purposes" stored vital elements that are in those leaves, things such as carbs, sugars, amino acids etc. that she has cleverly stored for future use in those leaves. This is why they will go yellow, even though she is getting good nutrition and is otherwise healthy. It is far more efficient for the plant to recycle these vital elements during flowering, than to make them from new, as making them from new will rob energy, energy that could be going into flower growth. This is what the "de-foliation brigade" fail to understand, removing healthy green leaves not only reduces your plants ability to produce energy, it also deprives her of those vital, cleverly stored elements that she needs to grow her best flowers. Hope this helps..... Organoman.