Monitor seems dark and out of focus Smile CA6748SL

Question

I have a Smile monitor CA6748SL and over time it has started to not be as good as it used to be, it is about 2 years old. The colour isn't as bright and doesn't seem very crisp like it is slightly out of focus slightly dark looking. Could this be that the tube is getting old and there is no hope for it or could it be a component has gone out of value and there is hope for this monitor. I don't really want to see it go as it is one of two identical monitors on a twin set up and I cant buy a replacement the same any more. The other monitor in the set up works fine and has a very crisp display. Is there a common component failing for this problem or does it sound like the tube is on the way out? I have tried adjusting the focus but can get it no better. Many thanks Sebastian