So sorry, the pics are too small for me to see. Perhaps someone else can see them better.

The first one looks to me like crab grass.

If it's the same stuff as what lines the roadsides in this area, it's Glandularia. Used to be included with Verbena, I think. If so, not native, but definitely ubiquitous! http://allthingsplants.com/plants/view/124328/South-American-Mock-Vervain-Glandularia-pulchella/

Becky: I think I see what the confusion is. The OP said he "just" had seed put down, and I had it in my head that this seed was still germinating, and in any case certainly is not long enough to mow. I reread his post and see that he said "in the last month" these weeds have been growing, which suggests the new grass is older than I thought. My bad. So given the grass isn't quite so new, I'd just pull the weeds out. I could get the ones in the photo in 10 minutes. I do hope the OP updates us on what happens. A little more on type of seed, etc. would be nice, too.