robinia shedding its leaves

Hi, Robinia is a tricky plant, it is a beautiful tree however for some reason unknown to me and any other professional I have asked on the matter, Robinia's are for some reason very tempermental and for absoulutly no reason they decide to act up without warning. I'm sure there is a reason you know, maybe somebody on this web-site will give you a logical explantion. All I know is that they are extemely unique and mysterious in this way, sometimes they last and sometimes they don't.

They do tend to shed leaves in summer especially if there is any wind and even twigs which are delicate. But it doesn't harm them. I usually have a sprinkling of the leaves over the garden most of the summer.

The leaves on my 10 year old Robinia tree have been shedding all year and have black spots on them. Does anyone know what the problem might be?