sorry I forgot to say it's a ghost pepper

Can you post a pic? Maybe to much humidity and it produced a mold or sun burn since no leaves were there to shade the peppers so that was a reaction to the sun.

sorry no pics but sunburn sounds very possible. Could you suggest a better method for drying them outside other than laying them in the sun?

You could try drying them in the shade / partial shade but if it's humidity that won't help, I normally dry my peppers in a dry cool closet strung up with some fishing twine

Just put them in a shady spot that still gets good air circulation. Be sure to cut them in half before drying also and lay them inside up on a tray or plate or whatever.
Bruce

I cut my Ghost peppers in 1/2 then place on a paper plate, cover with a paper towel and place on top of a bakers rack and it does fine. Though I may invest in a dehydrator later.

Yeah, its sunburn. Last year someone on a different board posted pictures of a mythical white bhut jolokia. Turns out the plant had fallen over on his hot deck and sunscalded.

Thats almost assuredly what happened to the ones you intentionally left out in the sun to dry.

Are they still good to eat if this happens