My few young mango plants were fine in winter but now here is spring in Australia some of them look like dying. Their leaves are wilting and leaves are dropped.
They look like they were growing lushly, then suddenly couldn't deliver water to the leaves. That's usually either an infectious condition to the roots, or waterlogged soil. I'd look at the roots and see what they look like. Another option is herbicide damage. That can do that too. There's no good test for that.
