Q.Ailing Southern Magnolia Tree
My magnolia tree began loosing more leaves than usual this year. There are spots on the leaves and some white spots on the underside of some of the leaves

Certified GKH Gardening Expert
This looks to be multiple fungal and bacterial infections. Usually, this occurs in soil that remains wet without a chance to dry out. It could be the luck of the draw with contaminated soil, though.
Fungicides will take care of the issue. These articles will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/ornamental/trees/magnolia/magnolia-tree-diseases.htm
https://www.gardeningknowhow.com/ornamental/trees/magnolia/magnolia-tree-care.htm