First thing to try is Weed-b-Gon Chickweed, Clover, and Oxalis Killer. Spray that on everything from the first picture and the last picture. Give it 3 weeks to work.

As for the middle picture, and how you got into this situation, I have more questions.

Where do you live?

When did you reseed? What month?

What seed and grass type did you use?

How did you water after seeding? How often and for how long?

How are you watering now?

Did you use a preemergent weed control either last fall or this spring?

Reseeded last year. Germination was pretty bad from the bag I tried. It was suppose to be tall fescue. Watered twice a day.

I am from Central Jersey.

Did not use any preemergent treatment this year.

Middle picture is hairy bittercress, a horrible weed that shoots its seed. It's too late to eradicate it this year because the seeds have already spread. I hate this stuff.

http://msue.anr.msu.edu/news/hairy_bittercress_a_weed_to_watch_out_for

The third image looks a lot like common lespedeza. It looks like clover, but it is a woody plant and usually it grows all from a single root. The lespedeza in my area straight up laughs at normal herbicides such as 2,4-D. I have found two applications of Triclopyr, about 2 weeks apart, to sufficiently suppress/control/kill the plants depending on how established they become.

owlnsr, I doubt those are lespedeza. the Google images for that plant does not match with the third picture. Is it another variant of chikweed?

As for the others, the bittercrest was growing in my backyard, close to by summer veggie garden; so I was reluctant to use chemicals. looks like they are all dead now as it is a cold weather weed (that is something new to me). The weed of the third picture seems to be the worst of all, spread all over my yard.

1. Chickweed, Stellaria media

2, Hairy bittercress or shotweed, Cardamine hirsuta.

3. Oxalis stricta

1&2 are annual, cool season weeds and are dying off if not already dead. But as noted, they have spread their seeds and so you can look forward to their return in fall :-) Might want to consider a late summer pre-emergent.

#3 will be handily addressed by the product dchall suggested.