We see very few blades of fescue lawn grass here.  Perhaps a lot of dead or dormant grassy weeds, such as nimblewill and crabgrass. 

If your lawn is more than 50% weeds, a renovation is recommended. Otherwise, weeds tend to outcompete new desired grass.

Whether you choose to overseed or renovate, the best time is late summer-early fall.  Spring is not the best time for new lawn to survive because it is still immature when the high temperatures and droughts of summer typically hit. (Which requires re-seeding in the fall anyway.) 

Aeration is also recommended in fall, because it leads to less weed competition. 

Though Preen is not labeled to kill tall fescue (lawn fescue), it does hamper growth.

Please read carefully through our page on how to do a successful lawn renovation and overseeding: https://extension.umd.edu/hgic/topics/lawn-renovation-and-overseeding

If you have substantial healthy tall fescue, you can put down a broad-leaved weed control product in May.

It's a great idea to do a soil test now. You can apply lime immediately.  To do a soil test, go here: https://extension.umd.edu/hgic/topics/soil-testing-and-soil-testing-labs    (Counties do not have soil test labs.)

Ellen