Does the mold grow on the seeds, the flesh fail to ripen properly and taste bland ? If it is, the disease is called internal blight. It is caused by a fungus that entered into the flowers and grew on the seeds cavity.

Were this grown near the Fukushima Reactors?

Hi,

To my knowledge, one of three pests is usually responsible for defoliating a young flush like that :
1. Bacterial black spot  (spray copper)
2. Mango Bud mite (spray with appropriate miticide)
3. chili thrips (many pesticide will kill these annoying fellas)

My suggestion is , If you have a 10x loupe, try and take a peek to see if there are little critters camping around the terminal shoot. If they arent any, then most probably it is #1.

Hope it helps.