North Dakota winter ruined my paint!

Gaston370Z

So I have driven my Z through a North Dakota winter without wrecking it, but winter still took its toll on my paint. After cleaning my car today, I noticed on the rear bumper and deck lid "dirty tiger stripes". So I get the clay bar out and start going over the car. Other than all the rock chips the paint is silky smooth, yet the stripes are still on the back. What kinda of cutting compound should I use to try and remove these dirt stripe? Its almost like the paint is stained. I plan on getting the car repainted in the next few years (bought it used and it has a couple small dents and the clear is spidered on the front bumper a little and some on the drivers rear. Anyone have their Z fully painted? How much did it run you?