It probably is a disease, and since you don't mention any spotting on the leaves that would indicate fungal or bacterial infections, I'm going to guess it is a viral infection. There are many viral infections that can infect peppers and at least some of them do cause symptoms that could be described as funky looking leaves.

If you have been having lots of rain, I'm wondering if that is impacting their production. I still get great production even when my pepper plants have funky-looking leaves, and generally I just ignore the lumpy, bumpy, crinkled leaves and the plants produce until they freeze in the fall.

Cornell Vegetable MD has great into on pepper diseases. I'll link it below.

My pepper plants' foliage has looked funky for the last month or maybe six weeks, but the plants are producing tons of peppers, both hot and sweet. We have had pretty low rainfall this year overall, though had a couple of good rainy days in early June that likely made the pepper plans pretty happy.

Sometimes when there is plentiful cloudy, rainy weather it seems like pepper plants just kind of sulk but normally they produce well in the long term over the course of the season after the weather gets hotter and sunnier and stays there.

I wouldn't give up on them yet unless they are in really pitiful shape.

If they are not flowering at all and not even attempting to set fruit, then maybe they need to be fed. Peppers are heavy feeders and sometimes have to be pushed along with fertilizer to get them to produce to their full potential.

Here is a link that might be useful: Cornell Factsheet: Virus Diseases of Peppers

Thanks Dawn,
Might try feeding them.Dumped worm poo on some of them the other day to see if that would help. Some of them are putting on peppers they just are not as big or thick walled as usual. A few of them died. Guess praying for rain has a stopping point!! What about spraying them with epsom salt. Heard it's good just never tried it.