I'm guessing that the flowers are on the 'good' tree. The 'bad' tree definitely has problems but I don't know what. If the leaves had just been yellow then I would have said 'chorosis' which is treatable. Hope someone around here knows what's causing the black spots.
Are the trees right next to each other? Depending on what's wrong with the sickie, you don't want the healthy tree to get infected. Can't tell for sure from the picture but it kinda looks like one of the trees might be too shaded. Sometimes it's better to have one really healthy tree and sacrifice the other. Don't want to be a bummer b/c someone here is bound to more than I do.
