Fairies & Rings of Fire
I think I like your fairies better than I like the locals, here.
Here's a selection of pix I took. Quite different symptoms
to those in your linked pix.
They're (sort-of) like a ring of fire. ??? The grass close to the center of the ring seems
to do OK. But it's hard to tell. The seeding rate was high and so the sward is denser
than average. That may have lead to an unusual softness to the turf as it might be
described as turf-bound. The clumps of surviving grass at the epicenter look coarser
than the general sward, but that may be because the plants-per-square area are so
much less in there. That - in turn - may be because only the rye grass has survived
whatever it is that's causing this problem and possibly killing the fescue.
I bought another bag of (the same) seed, some time back, to sow an additional area.
It looks (and grows) quite different. More than might be accounted for by the age
variation. It made me speculate that perhaps the bag I used for the main area had
a lot more fescue in it than the bag label indicated. The area was seeded Oct 2011.
I retired from this, quite a few years ago, so these problems are on my own place.
Despite the newly-grassed area being part of a free-range hen run for many years,
the whole property is inherently infertile, being a riverbed of long ago. But I've
applied a good amount of fertiliser and water is no problem. The grass is mowed
frequently and the clippings returned to the ground. Great for increasing the humus
colloid, but also provides a great medium for fungus development.