Hey marijuanavillebilly sounds like you have a good setup goin. Yellowing of leaves is common among some types of bud. I've seen lower fans leaves start to yellow up during the end of the 3rd week of flowering of a 9 week plant. As the plant begins to flower it uses all its stored up energy to form the buds. Usually you will begin to see the lower fan leaves turn yellow and gradually make its way up the plant. The plant no longer needs these leaves to survive so it drops them instead of wasting valuable energy trying to keep them alive. Sort of like a tree dropping it leaves in the fall.
As far as getting the best yield, I would try adding a molasses based nut to your feeding schedule. Also maybe try finding a good bud hardener to use during the last few weeks as well.
Also I would maybe lower your ph a bit. 7 is a bit high for a plant in the flowering phase, and a good flush never hurt a plant. Hope that helped a bit. Happy Growing!