His decline begin in 2014 when he did go on tour with Orianthi.
In this video () he seemed perfectly fine to me and a few weeks later he turned up in Australia and was a mess.
It had to do something with her I think.
In my opinion Richie has still a great voice (remember last year when he performed One Night of Peace) and when he gets his act together I am sure he can get back to his 2012 level.