Thanks for telling us where you are. Are you near the shore or more inland? North or south?

I'll try to help you ID the grass. What you have looks like something that happens to bermuda lawns. Does this lawn turn brown in the winter? In the summer does it get seed heads between mowing? Seeds like these fuzzy things.

What is your watering schedule? How often and how long do you water? Have you received much rain this summer?

When were the last two times you fertilized and what did you use?