This happened to me last year.  My tomatoes are in two old livestock water tanks that were past use as a water tank.  Put them behind the shed and filled with dirt. I should have used better dirt.

Anyway, I went to the store and bought some calcium tablets for an upset stomach. Also looked at the tomato wonder fertilizers at WalMart but went with calcium tablets. Take a little time and look closely at the contents.  I used the farmer version of a mortar and pestle (concrete block and a hammer) and crushed them to a very fine powder.  Put that in wife's watering can and dissolved the powder and watered plants.  It didn't save what was hurt but the later ones were just right.