The answer to 'aeration yellowing' is that it is a common issue that can occur after core aeration of a lawn. This yellowing is typically caused by the disruption of the soil and grass roots during the aeration process, which can temporarily stress the grass and cause it to turn yellow or brown. However, this is usually a temporary condition, and the grass will typically recover within a few weeks with proper care and maintenance.
The key to addressing aeration yellowing is to ensure the lawn is properly cared for after the aeration process. This includes watering the lawn deeply and regularly, applying a balanced fertilizer, and avoiding heavy foot traffic on the lawn until the grass has had a chance to recover. In some cases, overseeding the lawn may also help to thicken the grass and reduce the appearance of yellowing.