Hate to be the bearer of (possible) bad tidings but...
Have a really close look / feel of your sliders (fork lower section) around the middle, maybe hold a straightedge up along them. Wear caused by the lower bush can 'bell-out' the sliders over the bushes range of movement in normal running, -sort 'o halfway up. Makes a nice clattering noise.
No cure unless you can find someone who can re-tube them, the sliders are too thin-walled to bore out, not sleeve-able for the same reason.