Dying Photinia Red Robin
I have a large standard Photinia Red Robin which is approximately 15 feet high - in essence a small tree. It didn't do particularly well last year, but this year it appears to be dying. The leaves are hanging limply, have gone crisp and they are more brown than green. It looks awful. There is another smaller one close by which is doing brilliantly and has lots of shiny green and red leaves, as it should. In comparison, the tree is dreadful. There do appear to be growth tips but I'm not sure if they are still growing or not.
I'm desperate to save it - any ideas please?