The tree was relocated and it sprouted with leaves in the springtime, but the leaves all of a sudden are turning brown and falling off. Why is that? Too much sun or too much water? It has 6 to 7 hours of sunlight every day.
Most likely it is not enough water, unless you really have some problem with too much water, like after a rain it sits in a puddle for a few days. They want all the sun they can get, you just need to water enough to keep up with evaporation and remember, those fruit get their water from the roots, so if the fruits are hard and dry, they need more water.
Could also be root borer. There are some cures for that, but you need to catch it real fast because they will kill the tree in short order. Look for damage at ground level.