Apart from taking it to an auto-paint specialist, is there a good way to tell what caused it? I haven't yet taken a photo, but there are two spots close to each other. The top one is a nice symmetrical circle which makes me think it began internally - a stone chip would probably be an odd shape. About two inches lower - right where the bonnet turns under - it's an odd shape, but it's at a joint. There are no possible stone chips anywhere on the car.
I lived in the UK for 25 years and I used to accept rust as inevitable, but on a nearly new car in Melbourne it's unacceptable! I mean, you buy a new car for advantages like nothing going wrong for a while. I had been so impressed I had started looking at a Tucson/Santa Fe to replace my other car, but will have to put that idea on hold.