In general, disease patterns are usually random or scattered. Your browning appears to be in a pattern. There may be several reasons for the browning but we cannot say for sure. We do not know how your turf is managed. If you planted a contractors mix of different species some of the grasses may be dying out. Also, Some grass species can go dormant at different rates during hot, dry weather.
Brown patch is a summertime disease that affects tall fescue, rye grass but not usually bluegrass. This may have affected other grass species in your turf. See our website for more information http://extension.umd.edu/hgic/brown-patch-lawns
You may need to do some seeding this fall if the turf does not recover.