I had never heard of it either, but that's definitely what it is. It did show signs of yellowing after two sprayings, but due to the heat I've been pulling the remainder rather than damaging the fescue turf with excessive herbicide treatments.

Yes there were! Thanks to all! I believe I bought a hummingbird seed mix that had Nasturtium seeds. But I would say half are turning yellow and dying, and I think it's the heat. I don't have much shade, but I'll see if I can't relocate the remaining ones. It's a cute little plant! Thanks again!!

Looks like one of the Gnaphaliums. Cudweeds. I don't know which ones would be likely where you are.

Looks like pigweed, or another type of amaranth...also a lamb's quarter growing underneath its canopy. Both weeds you don't want going to seed.