I have a eucalyptus tree that is two years old and it is planted outside. The first two years it grew fast and beautiful. However, this year it has not grown at all and there are not many leaves on the branches. The leaves that are left are not healthy, some are brown and some a pale green. This year I planted two potato plants around the tree and they have spread around the tree. Could this have had something to do with the growth? The tree is about 15 ft. tall. Help!