I have been using Daconil about every 7 days or so since I planted my tomatoes. I had some symptoms of early blight and the spraying seemed to keep it in check. Leaves and plants were doing fine...........until I got home today. I noticed that almost every plant has some yellowing or browning leaves at the bottom of the plant. The newer leaves are fine with no wilting. We have had very hot and dry weather but I have been watering every other day or so. Does this sound like a normal transgression of an aging plant?