Yellow leaves late stage flowering

She is going into senescence. It is typical for the plants to cannibalize at the end of flower using the sugars in their leaves that causes that fade we're all looking for. That said, if it occurs too early due to lack of proper nutrients, then your quality and yield will likely suffer. When they use up all the sugars it leads to a smoother more pleasant smoke. Have you ever burnt sugar? It gets thick, black/brown, nasty and carmelizes. It's all about balance and feeding you plants the right nutrients in the correct ratios at the correct times. A good flush helps you achieve that coveted white ash. This is the best of my understanding, but I am always learning too. Good luck and happy growing!