It's growing great guns, but the leaves underneath the primary growth are spotty and brown and withering, only the new growth looks really healthy. I have a little window herb garden, the oregano and parsley are thriving on the fairly light Miracle-Gro nitrogen formula I'm feeding them, but the basil isn't happy. Am I overfertilizing? Underfertilizing? Is there some kind of fungus involved? HALP, GT GARDENERS. TEACH ME.