Im on my first grow, so take my advice with a grain of salt, but mt fan leaves have been dying since about their 3rd week (from the bottom up). My secondary growth still looks good and the plant is really healthy. I dont think its a problem at all. A more experienced grower might say otherwise, but i dont think lower leaves are all that important after a certain point. Good luck.

Oh yea, Im using a 85w cfl and 4 tubes, so we have like the same grow goin. I also didnt use fert till 6 weeks in. Holla @ yo boi.