Bananaman88

When I first read your post, the first thing I thought was spider mites, but then I saw you were growing it outside, not indoors. While that, in and of itself, doesn't necessarily rule out spider mites, they are usually most troublesome indoors. What I noticed was that it is the lowermost leaf on your plant which has turned brown. As the lowest leaf, it is also the oldest, and therefore likely that leaf has just died. This is a perfectly normal thing and as the plant gets older, you'll likely see the lowest, oldest leaves die off as the reach the end of their useful lifespan. Nothing to worry about unless you see it start to happen at an accelerated rate or to other leaves higher in the canopy.