The actual grass, you do have, in those photos, are much too good to be Bermuda. or , any other Southern grass I've seen.
Whatever you have, that, what, is still alive, in the photos,, needs to be alive , and, in the bare spots, as well...
If it's ,Fescue, I would not be looking for what makes it go... so much as... What made it stop.
Find out what happened in the "Kill Zones", and go from there...
Now that I know that clay's texture(platelets) has nothing to do with water infiltration, percolation, or drainage,,, I wonder what does...