Answer: If only the fruits and not the leaves are affected, and if the black spots are on the bottoms of the fruit, I'd say your plants have blossom-end rot. This is the result of a lack of calcium or a surplus of nitrogen tha't blocking the plants' uptake of calcium. It can be caused by irregular watering, too, which restricts calcium uptake. To prevent, make sure the soil is kept evenly moist (no wide swings from very dry to very wet). You can reduce evaporation of soil moisture by mulching around your plants. The affected fruits are edible, just cut off the affected portion.
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