Especially with a year like this with heat stressing many plants, I don't think it's too unusual to have a few of the lower leaves brown as they are the oldest and are being shaded by the top growth. HOWEVER, if it starts creeping up the stem, then you need to hit it with a fungicide, pronto. Those areas with no mulch are more susceptable to fungus being splattered up from the soil during watering or rain.
As Lorn mentioned, the purple leaf is a mystery. I hit mine with a fungicide and the new foliage seems to be all green since then, though it could be coincidental.
