Last October I planted a tree from an apple seed. I am keeping this tree in my house. The tree is thriving and is almost three feet tall now! My problem is that every now and again some of the leaves get dark brown spots on them. they still seem healthy (except for one which fell off a few months ago) but it appears to be getting worse. one leaf is almost totally brown now. and four or five more have been infected. I do not know much about plants so I have no idea what I can do to help it. PLEASE HELP ME!?!