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it sounds like flower end rotit sounds like flower end rot to me. I had it really bad on my tomatoes last year. it's aparently common to tomatoes, peppers and some squash. my research told me it was due to a calcium deficiency, and that in most cases the soil has enough calcium, but the plant is unable to absorb it usually due to not enough watering, or irregular watering. I've watered my garden more consistantly this year and have not come across any black spot, or flower end rot so far.