Single small brown patch in thriving lawn

[Sublime440]

I have been careful since last fall to care for my lawn all through the winter and now spring and have noticed a small (maybe 8" diameter) patch of grass that is slowly dying. We haven't had decent rain in over a week but the rest of the lawn is fine. I would think it's too early for "brown spot fungus" or whatever it's called and thought it was too early in the season for that. Also, it has not been humid and there is no significant dew on the lawn in the mornings and night temperatures haven't been 60 deg or above for several nights straight yet. I don't want to take the wrong action or not take any action and have spots show up later in the season.

I live in middle TN and have fescue. The last time I fertilized was in mid March and I added lime a few weeks ago (put lime down last in late fall). I can get a picture if it's absolutely necessary, but just imagine a nice fescue lawn with a small spot starting to die. If it helps, I have seen this before with large rocks just under the top soil that kills the grass once it gets hot and dry but I haven't checked for that just yet. I didn't know if it could be grubs, fungus or something else.

Thanks for any advice.