Why are the fruits of my chili plants turning black? The plants had capsid bug, which I treated first with a mild solution of washing up liquid and second with a bug spray. At that time the plants were indoors but then I put them outside. They have since improved and look quite healthy and have lots of fruit coming on them except that the color of the fruit is turning black.
If the black is on the top or side of the fruit, then it is likely sunscald and is from too much direct sunlight. A simple shade will help stop it. If it is on the bottom of the fruit, then it is blossom end rot. These articles will help: https://www.gardeningknowhow.com/edible/vegetables/pepper/pepper-sunscald.htm