Answer: There's an insect pest called cherry fruitworm that burrows into the berries near the stem, causing the berries to shrivel up. Examine the shrivelled berries carefully, looking for the small holes and/or fine webbing that will indicate the presence of this fruitworm.
Since the worm burrows, it's difficult to control once it's established. The adults are gray moths with black spots, and they lay their eggs on the berries in mid-July. Since you have only two bushes, you can try inspecting the plants daily, destroying any affected berries. Be sure to clean up around the plants in the fall, and keep the plants mulched, to help deter overwintering.
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