Emerging weeds post over-seed
Left photo - This looks like deadnettle, a winter annual weed.
Middle and right photos - looks like deadnettle and hairy bittercress, winter annual weeds.
Here are our webpages on these winter annual weeds and management in the lawn. Shade and mowing the lawn too short are conditions that favor this weed. https://extension.umd.edu/hgic/topics/deadnettle
If you have small patches, you may be able to handpull or dig the weeds with a weeding tool. Since the lawn is newly seeded, you will have to wait until you mow the grass about 3-4 times before using an herbicide to spot treat the weeds.
Here is more about lawn care after seeding https://extension.umd.edu/hgic/topics/care-and-maintenance-after-seeding