I live in San Gabriel, CA and planted the tulip tree one year ago. It has taken well and the leaves are blooming until this past week when I noticed the bottom half of the tree’s leaves are covered with large dark brown spots. The tree is well watered, has mulch at the base and I used Jobes spikes to fertilize it last month before the leaves started budding. Is this mold or aphids or what? I don’t see this on my neighbor’s tree up the street albeit they are 11 years old and mature. Could it be my sprinklers are getting the leaves wet and causing the mold? I’m a bit clueless and not totally familiar with this tree yet. Thank you. Fred K