Question: Why are the leaves of my magnolia cupped downward? It also isn’t growing properly.

Answer: That usually points to some type of weedkiller damage, most likely from a granular weed-and-feed product. Think back to what has been applied in the past, especially 4 to 6 weeks prior to your first noticing the cupping. Keep the tree moist. Otherwise, there is no antidote that you could add to the soil.