A simple quick fix is to drill a very small hole in the underside of the headlights. Your headlights most likely have alot of moisture built up in them, hence the foggy/yellowish look. The small hole will allow the moisture to escape (note: you should bring your headlights into room temperature) and you can seal the hole back up with silicone.
If that doesn't resolve anything, you may have to bake your headlights in the oven to melt the sealant so you can clean the inside of the lenses. It sounds like your problem is more along the insides of the lenses rather than the outside (which you should also polish up as well).