Every spring, I buy new basil for my raised bed herb and flower garden. (I am in zone 6.) It starts out robust, full, the leaves are rounded/oval and a rich darker green. This year's pot, which I just planted, is especially lush and beautiful. I read that basil does not like to be watered from the top getting the leaves wet (difficult when it rains ;~]), so my sprinkler/soaker waters it at a lower stem or soil level. No matter the watering system or that I feed it properly, every year the leaves fade to a pale green, become narrower, spade-shaped, and grow spaced further apart. Why? What am I doing wrong?