In alot of strains, leaves begin yellowing and dying off mid-flower. If nothing else, they will in late flower as your babies suck up all the unused Nitrogen from the leaves.
It's perfectly normal, and trying to fix it with a boost of Nitrogen is usually looked down upon, since most people want yellow leaves mid flower. They want them yellow and give less N to them because it loses alot of the chlorophyl(green color) the plant has, and makes the curing process considerably shorter since not as much chlorophyl has to break down into sugar.
P.S.- Buds look great you guys, hope you both have a happy harvest.
