You can come into the garden center for a lawn fungicide although they are better used as a preventative earlier before the disease shows up. The rainy summer we’re having is adding to your woes since this is just what the disease loves. Keep the lawn taller (like 5″ or so) since mowing short helps the disease. Once it cool’s off a bit in the second half of August, feed the lawn and again a month later. Let the lawn get a little taller next summer and hopefully it won’t be so wet and the disease will subside.