Good Morning,
Unfortunately, it is nearly impossible to diagnose turf diseases in this forum. I recommend contacting MSU Plant Diagnostic lab. Please start by emailing your question and pictures to them. Include info such as when and how much you water, when you lasted fertilized, what other chemicals were applied and when. If they need a sod sample they will contact you. https://www.canr.msu.edu/pestid/
Using a hand lens looking at your grass blades, and comparing to the diseases here, you may be able to spot something.

Turf Diseases - Turf
As you can see, the possibilities are many, and a close examination of grass blades under magnification is usually required.

The Plant Doctor: Large (Brown) Patch of Warm-Season Turfgrasses | Mississippi State University Extension Service
ppfs-or-t-12.pdf

Also remember brown lawns are OK; dormancy is a natural response to drought, however, some water may be necessary during an extended drought of more than a month Go Green Lawncare Tip Sheet - MSU Extension

I hope this helps. Thanks for using our service.