I can see mulch touching the trunk. Mulch touching trunks, often, during rainy weather or trunk-wetting irrigation, encourages trunk circling roots, and sometimes infections in the bark.
The products I mentioned are not "organic." If your tree is not going to be productive because it is dying, certification for organic production is mute. If you save the tree, the contamination will be broken down or diluted greatly by the time the tree does produce, 2-3 years later. And if the tree was produced by any of the major mango tree production nurseries, it wasn't organicaly produced.