This happened at the end of the season last year too but I seriously had no idea why so I planted in the same spot this year. I am LIVID! My tomatoes are smaller and they are "bad bottomed" sooner! WHAT IS THIS?!
I should also mention that on the opposite side of where my tomatoes are my peppers...and this is happening to THEM too! I treated the ground for grubs WELL before (a month or more) I planted.
If I lose everything I planted I think I might cry. :(