Full in bloom, why none of them, becomes a fruit?

庭のライムの木は満６歳、この家に引っ越してきたお祝いに苗木をいただいたものです。それから毎年この季節によい香りの白い花が満開になり、小さな実までつけるのですが、それらは遅かれ早かれ例外なく落ちてしまいます。だから今年も期待薄。木が自分で実を育てる能力がないと判断して実を落とすのだそうですが、肥料も水もたっぷりやっているのに何がお気に召さないのでしょう？お隣のレモンも金柑もちゃんと実をつけてくれるのに。

My lime tree is full in bloom now, as it usually is this time the year. Although it gets hundreds of fragrant flowers, none of them has ever become a decent fruit since I was given this tree as a house warming gift 6 year ago. It duly bears hundreds of tiny fruits, but ALL of them eventually drop. I heard that a lime tree decides to drop whatever fruits it cannot afford to keep.. is it unhappy? Does it demand more water, sun, food or more attention? I really want to know why since the other citrus trees next to it, a lemon and a kumquat, are happily bearing nice fruits each year.