Problem with large cotoneaster
I have a large old Cotoneaster frigidus 'Cornubia' ( I think). It is about 14 foot high with very attractive architectural type stems and a lovely canopy overhead, so is a great centrepiece for the border. It has been happily growing for the last 22+ years. However, this year I have noticed a lot of dead patches at the ends of branches with brown, dead leaves and some bare branches. It is also not as flower heavy as it usually is. I am used to it being semi-deciduous, but these are clearly dead patches. I am going to get up there and prune them out but I wondered if anyone knew why this has suddenly happened to it? has it been stressed by the weather this year or is it coming to the end of it's natural life?