Good Morning Charlotte,

Based on the photos you sent there is a good possibility that you are experiencing Ascochyta Leaf Blight. This condition often occurs in blue grass lawns where there has been a wet period or over watering has occurred followed by high heat. This fungus does not kill the lawn and should recover over time. I am adding a CSU reference on Ascochyta Leaf Blight (https://extension.colostate.edu/topic-areas/yard-garden/ascochyta-leaf-blight-of-turf-2-901/). With the lack of natural precipitation in the Broomfield area and the high temperatures the lawn could be experiencing some drought stress (note difference in shaded part of the lawn). You may want to check to ensure your sprinkler system is applying the right amount of water to the lawn. I am attaching a link to the CSU Operating and Maintaining a Home Irrigation System, 7.239 (https://extension.colostate.edu/topic-areas/yard-garden/operating-and-maintaining-a-home-irrigation-system-7-239/).  If you have additional questions or the condition persists or worsens please contact the Broomfield Extension office (email address: <personal data hidden>). 

Mike