My 2011 MN has got this on the bonnet too, just recently. I think it is from the excessive heat from the turbo/engine. I'm going to just remove it, re-spray and maybe do some graphics seeing that I already have them up the sides. After all, it's just a 4x4 that will get scratched, dented and mistreated by its user.
]2011 MN Triton 2.5 diesel, canopy, roof basket, Aux. battery & 80W solar panel, reverse camera, UHF, SatNav and in-car DVD to keep kids quiet. Bullbar with Runva 9500lb winch, 2 inch EFS lift, custom vinyls and LED light bar.