@Hooper - Hi, Denver here, about 5400’. Yes, have had some problems this summer. We had our lawn redone (stripped out, resodded) about two years ago. Last year everything was fine except for a couple of hard soil spots. This summer, areas in the front that are high sun exposure started to develop brown spots, mostly small but a couple of moderate size (2 sq ft or so). Had our arbor guy stop by and he said it was a fungus called “ascochyta leaf blight” and was showing up all over town. Odd thing was that none of our neighbors had it and our back yard was fine (less sun though).
I started a fungus treatment program (every two weeks) to stop it and just this last week have cleaned the dead grass out of all the spots and seed patched them. We’ll see how this goes. Next season I’m going to do a prophylactic fungus treatment at the very start of the season just in case. Don’t know if this is the same as what your seeing.
Just noticed your post was from June. That’s when all this started for us as well.