Its just simple corrosion and it lifts the paint into a bubble. It's water ingress from somewhere (not electrolytic corrosion from steel to alloy) and then it carries just like on alloy wheels (best seen on diamond cut and lacquered like the LMGT4's). Nissan should really cover it but as it is coming up to the end of body warranty period and the fact that bonnets will have stone chips they get out of it.
If it comes from the seam on the bonnet folds you can use a seam sealer like sikaflex and them paint the bonnet and it should last a little longer.
I have had my bonnet painted once and issue never came back