Sadly there's no real way to date lead bullets like those. I can't even tell from the picture that the one on the bottom right even is a bullet, it is so mangled. The bottom left one looks somewhat modern, but again it is really squashed. The top left one certainly looks like it could be 19th century, but similar bullets are used to this day, and that level of patina could have occurred over 30 years or 100+ depending on soil conditions and other factors.
No clue on the really big one. My gut says it is not projectile related.