Gosh have to admit I haven't a clue! I've always thought they were just about impossible to kill. Could you become member of GoY so we can ask a few questions guest. Such as did it get very dry or very wet during the year? Has something else changed in your garden? Did you accidently get a systemic weedkiller such as Roundup on it?

They always lose leaves in Winter. So dont worry

Yes Poaannua is right. Mine has all but 'disappeared' but will come back with avengence in april/may next year. It is lovely for early autumn colour and then drops all its leaves around November.