Could be a number of things, including that it went dry at some time recently, or simply an old leaf.

Can you post images?

Also give us more history -- in the ground or pot? Fertilized or not? If so with what? How and how often do you water?

This is the whole plant. In a raised bed. Planted mid March. Once a month fertilized with Tomato fert from Miracle grow. Spray and a couple quarts towards bottom of plant. I water drip system every 2-3 days if no rain. There are 3 plants, this one is the only one affected. It has peppers on it, but I noticed it has no new flowers. All 3 plants had performed great. Used fungicide last 3 weeks with no luck.
Some peppers that were on it turned red. Hope these pictures work.

plant
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pepper
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leaves
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