Leaves on Basil turning brown
I'm having a problem with my basil - the leaves are starting to turn brown from the center outward. They aren't drying up, but rather it almost looks like it is varigeted now. Here is a picture I took of a leaf I picked:
My plants are in a spot that gets about 1/2 day of full sun, and they have gotten watered a lot lately. Is this due to overwatering, or is this some kind of disease? If its a disease, what can I do to treat it.