Magnolia Tree Problems
Your magnolia is most likely due to transplant shock. Magnolias are susceptible to this. The change in light, soil, roots, etc. is somewhat traumatic to the tree. Leaves should replace themselves as the tree becomes more established. Soil should be moist like a wrung out sponge. Soil pH and texture could affect the trees health. Give the tree a little time and monitor its progress.
I hope this helps,