Heyy Green!! Very nice plant you got there!👊👍 The lower leaves doing that is a normal thing at this stage of flowering. What the plant is doing is putting all its energy up top where all the bud sites are and thus the lower leaves get what they have in them sucked out and yea die off. Nothing to stress about. The plant looks very healthy great job👍 So all there is to do is when they either die off or get to the point of the one in your pic. pluck it off. but nothing to worry about 👌 Happy Growing!!