WHATS WRONG WITH MY TOMATOES.
Thanks for writing. There's a condition called "green shoulders" on tomatoes and that's what it sounds like is going on in your garden.
Green shoulers can occur if nighttime temperatures stay too high for extended periods while the fruit is ripening, if the fruits get too much direct sun on them as they ripen, and it's much more common on certain varieties than others.
---Justin, Senior Garden Editor, BHG.com