Trees – Fertilize to Improve Fall Leaf Color

My wife and I are now in our second fall in our home in Auburn, GA (near Winder). We have about 1/2 acre of woods behind our house, including oak, maple, elm, sweetgum, hickory, and other deciduous trees as well as some pines. The trees predate the building of the neighborhood, and appear to have established themselves naturally, rather than through intentional planting. Williamson Creek runs along the back of our property, through the woods. The creek is down a bluff/hill making ground level 10-20 feet above creek-level throughout most of the woods.

We have expected some interesting coloring in the fall, yet the leaves turn dull yellows or brown then fall off. The soil in the woods seems to be composed mostly of detritus from the trees (lots of pine, for sure) but becomes predominantly clay if I dig down a few feet. The clay is more yellow/gray than Georgia Red. I expect that the overall soil pH to be acidic from the pine presence, but have not had the soil tested.