If you are seeing very consistent circles appearing in your turf, especially after a mowing, then you have firing.
Firing is that burned or yellowed look that can appear after mowing. This is caused by removing too much grass blade at one time and thrusting the turf into severe desiccation and water loss. Also, a dull mower blade can also cause firing because the blade tears the turf blade instead of making clean cut again resulting in severe desiccation and water loss in the turf blade. Closely mown warm season turf requires an increased mowing schedule during periods of heavy, rapid growth if it is to be maintained at a short height. A 3 – 4 day mowing schedule is often required along with increasing the mowing height of the mower.