I'm looking for a close up of a almost dead blade. If confirmed to be brown patch, quit watering and do not fertilize. This years rainfall has really let the funguss thrive. Brown patch is very common and incurable. Most of the time it's so insignificant it can be blown off with higher mowing. You're a little past that. A good fungicide needs to be sprayed at weekly intervals (follow the lable). Youre lawn wont bounce back you'll want to overseed and aerate in the fall And spray it again next year around June to halt its presence in humid weather. Stay way from nitrogen in summer weather. Brown patch likes constant wet soil nitrogen heat and humidity.