Are they potted or gardened?

Potted on a balcony in DC. Many pics on this thread.

Sounds like a root problem. Common with smaller pots that have rot and are becoming root-bound as well which doesn't help. You have to look at the roots and see if the roots look rusty. If they do, then you might have to refresh the soil and clip the root ball of all dead looking roots - gotta be thorough, because if it is root rot, it will spread again and very quickly. I have had this very condition crop up last year. Lost two plants, but saved a third.

Don't worry about the fruit, it's usually the last to go. But you have to get on it asap. Detangle the root ball as best you can keeping the roots wet the whole time. Inside a pail of water is ok or on a tarp with a makeshift 'puddle' will do as well. Then snip anything rusty or dead looking, you'll be able to tell easily. Replant into fairly moist, but not too damp or soggy, soil. It should be like that of instant potatoes that haven't quite got enough water.

Replant and hope.