My vote is either over or under watered. If it was a nute deficiency, I'm not so sure the plant would have an easy time putting on that much fruit.
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I have a plant that constantly gets under-watered, mostly due to its location and my lack of being around there, and it looks like that. Usually doesn't drop young fruit though, but fruit ripens small.
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Just my thoughts
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How long has it been in that pot? Can you take it out by the trunk? If so, how do the roots look? White, yellow, seemingly vigorously growing, seemingly slow growing, etc?
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