I've got an Olive that's been on my south facing roof garden for a couple of years and appears to have caught some kind of black spot.
The inner leaves are one by one developing small black spots. Maybe one or two per leaf. Over several days the leaves turn light green then yellow and fall off.
In March I did 'hide' it between two conifers for protection against some heavy wind and rain for about 5 days (quite a shady damp place) after which the symptoms appeared.

It's a healthy tree - doubled in size in 2 years (about 1m tall) and has got many flower buds that are about to bloom.
With all this leaf drop (about 5-10% so far) I'm worried about it lasting much longer.
Am about to treat with a fungicide (Dithane945) - is that a good idea?