rotting plum tomatoes
I have several varieties of tomatoes that are doing fine with the exception of the plum tomatoes. I can't remember what variety they are (I'm new to this). The plum tomatoes look wonderful on the outside - smooth red skin without blemishes, but they are all rotten on the inside. I tried cutting open a green one which was fine, and an orange one which had a small spot of rot, so the rotting is happening during ripening. Any ideas on what is causing this or what I can do to fix this?