Somebody who knows about mangos has told me that a young mango to be planted must have tiny buds and purple leaflets at the top, a sign of growing. It it looks like that, some grown leaves dry at the end is not a worry, only the soil must be ample, not rocky, and must receive plenty of sunlight. Must not receive much wind when young, and must have plenty of water if it is in full sun. In short, it is the top that shows the vitality of the tree, and not the big leaves.