Q.Little Gem Magnolia
Planted earlier this year in late spring. First flowers are turning brown before full bloom. We have had a lot of rain this season. Could too much water be the culprit? Otherwise, the tree is doing well.
"Little Gem" magnolia will tolerate most soil conditions, including sand, loam and clay, but prefers a slightly acidic pH.
All magnolias need daily watering after planting and weekly supplemental watering for the first couple of seasons. Fertilize in spring with a mixture of milorganite and a slow-release general fertilizer.
Flower and leaves can drop under stress and certainly heavy rain can be a cause of this.
https://www.gardeningknowhow.com/ornamental/trees/magnolia/magnolia-evergreen-varieties.htm