Any guessers? Front lawn is struggling!

I think I have a bug issue?

I made a few mistakes at the start of the season. I aerated late. Didn’t apply any pre-emergent (the weeds this season highlight that nicely). My first fertilizer was IFA step 3, 6 weeks ago.

I thought it was just the heat in peak summer season, but when I tested the soil for moisture levels, I began to see very tiny black beetle type bugs in the dead patches. They’re extremely small and hard to capture, I finally got one on the concrete to take these pics.

I put down Sevin insect killer and that has not killed the bugs. The dead areas have expanded over the weeks and the grass looks unhealthy.

I acknowledge I should have taken much better care prior to this, I’m planning to spend time this fall to reseed but I am a little worried about how to resolve this in preparation for the upcoming cool season.

Any thoughts on what this tiny bug could be, and if it’s to blame for my pitiful lawn? I also wondered if it was fertilizer burn from when I put on the ifa step 3 spring and summer mix down 6 weeks ago. It’s been slowly getting worse which leads me to believe it’s a pest issue.

Any thoughts or suggestions welcome, thanks in advance!