I believe my problem goes beyond the rail dust that was collected upon delivery as I removed that years ago. It seems to be more of an ongoing issue, I've seen it come back a few times and the lack of wax doesn't help. Also as seen, if you let the problem go unoticed it can become quite severe.

I'm not sure if this is a Silver issue, but have a feeling that Silver not only shows it more, but the metalic paint might also attract it. I would say if you own a silver X, it would be best to wash and wax more often.