Hi Alvin,

I'm sorry to hear about your lawn!  I think you may have two things going on.

the large brown patch nearer the fence has the hallmarks of Ascochyta leaf blight, though it is a bit late in the season for it to develop.  I would need close-ups of the transitional area of the lawn, where it's going from green to brown, to better be able to diagnose if that is what is happening.  This fungus establishes in early spring, but symptoms develop when conditions become hot--the plant has extreme water stress and you end up with big patches that look dead.   If that is indeed the issue, the good news is that it is usually fixed by adjusting the sprinkler system, and the grass is not dead below ground.  With the restoration of adequate water, it usually resolves within a couple of weeks.  Water, rather than fungicides, are the recommended treatment.

The other area, with the ring-shaped dead patches, could be a result of necrotic ring spot, a different disease.  It is also favored by wet conditions in the spring, and heavy fertilization can make the problem worse.  Fungicide applications in the spring (doing it now will not help) can mitigate symptoms, but it is difficult to manage.  Keeping the lawn on the drier side in the spring can help--and waiting to fertilize until June.  

One of the easiest remedies for necrotic ring spot is to overseed the affected area with perennial ryegrass, which is immune to the disease.  Its texture matches that of Kentucky bluegrass and it will fill in where the bluegrass succumbs.  

I hope this is helpful!

Cordially,

John

Thank you!

To rule out stress caused by irrigation (and disease that can be aided by that stress), you might consider conducting this irrigation audit, paying particular attention to that large dead patch.

https://extension.colostate.edu/docs/pubs/garden/irr-audit-tutorial.pdf

It may be solved as easily as making some adjustments to your sprinkler heads.  Please let me know what you find!

Cordially,

John