A couple points:
This is not brand specific. If a tractor sits in the sales yard for a couple months, there will be rust on it. The tractor will get some scratches during shipment or at the yard as they move it around and those spots will rust. Any where water can sit will tend to rust.
Bewere of any chemicals you may be storing in your garage even if you think they are in air tight containers. Pool chemicals can turn metal stored in the same room into a pile of rust in just a month or two. Salt for your driveway can have an adverse effect too, albeit not as dramatic.
Finally, it may also be that you've gotten an especially poorly painted tractor. It happens with all brands once in a while, just like it can happen with a car every once in a while. I think you should ask you dealer about it, but I wouldn't get your hopes up on that one.
Oh, I guess that was three points.
Cliff