I don't know exactly but I have a couple guesses... could you post a picture of a closeup of the flower bud? Obviously, an open flower would make it easier to ID. How sure are you that all of the pictures are from the same plant? (It may be the angles of the pictures deceiving my eyes). You could also post this on the Name That Plant forum where more eyes would ID it.

Some of the pictures look like lactuca serriola, and some kind of look like oenothera biennis.

The top two and bottom two look like different plants.

I am also not certain they are all the same plant.

Check Erechtites hieracifolis. Some of your plants could be that.