The lower leaves on my basil are turning yellow & falling off. The top part of the plant is growing; it has a bloom at the top & quite a few new leaves near the top. Only the bottom part is affected. The leaves become a little limp, start turning yellow (they also develop faint gray spots) & sometimes fall off, especially if you touch the plant. The bloom developed after this began happening. Should I top it & remove the bloom?

I've checked for pests & only found some small fly-like creatures. I read that these were caused by overwatering, so I cut back on that & sprayed the plant with Safers. This was about two weeks ago. The bugs are gone but the basil still looks bad. Thanks for your help.