Hi it is all over my backyard. Took the picture today.
A close up. In the middle of the picture.
I'm seeing that weed, too, but not as much as in your first pic. It seems that Preen doesn't stop and I'm also wondering what the heck it is.
Don't know what it is but it spreads FAST. I only had success by pulling it out in the center to get the rootball and picking up any stray pieces. Almost eliminated it after only 2 seasons.
I believe it is chickweed. I can't see it real well, a close-up would help, but you can Google it and check it out yourself.
If it is chickweed, it is edible raw or cooked. After weeding, take the green tips for your soup or salad and dump the rest on the compost pile.
Here is a link that might be useful: Video (not by me) with recipe ideas
It's mouse-ear chickweed, Cerastium fontanum.