My backyard has been growing nice grass. I mowed and watered it for years no problem but now it has three bare spots, yet all around these spots is good healthy grass waiting for a mowing. I fertilized it last winter, raked it in and put seeds down this year...nothing. I put down Pennington grass seed with the promise that this will grow grass...nothing. I'm tempted to put down sod just to cover the bald spot but I'm sure this would just wilt away.
Certified GKH Gardening Expert
If it is happening in spots, then you likely have a fungus. Which it is would be hard to say without knowing the symptoms, but this article outlines the most common: https://www.gardeningknowhow.com/lawn-care/lgen/grass-fungus.htm The best thing to do is to treat the lawn with a fungicide first and then reseed the bald areas.