Normally my soil drains too well as I'm just below the brow of a hill and is very dry by the end of summer. Some parts have clay, other bits are shallow soil over rock. It could have been phytophthora, no sign of honey fungus though. All of the plants flowered well and leafed up, then late spring to mid summer the leaves wilted and dropped. In some cases the bark on the main stem/stems had split and easily came off.