I had a customer call me the other day saying that some spots of their lawn was turning black. I took a look at it yesterday and they said that it had gotten better after the rain the night before. THey said it looked black from a distance but looking at it up close it didn't look bad. This area is baked on by the sun all day and is somewhat in a valley. They do have a sprinkler system they use often. I din't see the blackness but in the areas they showed me there was a slight difference. I did notice whoever is cutting their lawn is using a dull blade. Their was also some brown spots on the blades of grass. The rest of the lawn looks great. I think this all started when the temps went above 90 with high humidity. some sort of disease or fungus I'm assuming?