Any weed killer of any sort used anywhere in the vicinity?
Including next door or down the street?
Also including any weed-and-feed stuff for the lawn?

some of my tomatoes are doing the EXACT same thing. Someone here said it was herbicide, but none was ever used near my yard. I have 50% of my plants in the ground, and 50% in pots/half barrels. The pots/half barrels got manure added to them, the in ground ones didn't. In ground plants are fine, as are pots with no manure added, so I'm guessing my manure (sheep) was too fresh/strong. Sound possible for you,too?