I have just received my license so I am at "ground zero" trying to identify problems with lawns. I am attaching several images of a mature lawn that has never had any disease or pest for the past 12 years. It is fertilized 2-3 times a year and cut every 7 days at 3". The problems started 3-4 weeks ago when I noticed an area with considerable damage. It has not started to spread to other locations in the lawn. I would appreciate any input as this is my yard!