Lawn dying off in patches

Lawn dying off in patches

We bought our new home this past December-sod was put in for the grass-I believe St. Augustine. We're in Central FL, so it's just started getting warm (low to mid 80's during the day), and I'm noticing that there are areas of the lawn that are dying off. We've got beautiful green grass over about 80% of the lawn, but there's a patch about 6' x 8' in the back of the house, and all along the front flower garden (about 2' x' 8') that are turning brown. We've treated for bugs (fire ants/chinch bugs/etc.) and fertilized with a fertilizer specifically for our area and grass type and had no luck-although the green areas are getting greener... Anyone have any ideas what this could be? Thanks! Tracy
My garden part 1

My garden part 1

A hardy caladium

A hardy caladium

Raised Bed Garden!

Raised Bed Garden!

One big ol’ mix up of thrifties!

One big ol’ mix up of thrifties!

3…2…1…

3…2…1…

what do you think?

what do you think?