I see damage like that occasionally in my zoysia lawns. I have used Prostar with limited success in the past. Pretty much a "crap shoot". It seemed to depend on what specific organism was causing the fairy ring at each particular site. I never used the Heritage until this year even though it has been around for awhile due to the expense. I rarely find the need for fungicides and I couldn't see spending $400+ for something that I would have sitting around for the next 10 years. I was informed this year by my supplier that they would have Heritage packaged in a granular form. One bag would cover about 12k at a cost of about $80 if I remember correctly. Being granular it is quick and easy to apply. That's a lot of Fairy Ring that can be treated with one bag considering most look like the ones in your pics. Occasionally I'll see one that is longer with less arch. The longest one I've ever seen was about 100ft long. I've used it on about 7 separate cases this year. Most sites had multiple rings with some being more severe(pronounced) than others. I've seen excellent results in each case. I don't want to stick my neck out and use the word "cured", but I am seeing excellent recovery in the more severe cases and there is no sign that Fairy Ring was ever present in the less severe cases. Sorry for the book. Just trying to relay some personal experience.