There are two main contaminants your car will pick up, tar based and iron based. Tar remover will deal with the tar which tends to be black sticky marks on your paintwork. Iron, you cannot see until, like has happened to you, it starts to rust and then becomes very evident, espeically on white paint paint.
With your car being new, it is actually the most common time to see such high levels of iron due to how the car is stored and transported in a very industrial fashion. The other main place you will pick up iron deposits is from a railway line, do you live close to one? If so you are likely to get more going forward, if not it is likely they are just from the transportation.
It is easily dealt with though, something like this -
http://www.polishedbliss.co.uk/acatalog/auto-finesse-iron-out-cat6.html - will sort it out for you very easily. There is no damage to your paintwork and nobody has done anything wrong. Just be aware if you are going to wax/detail your car at all, you should make sure you carry out a full decontamination, including iron and tar, as part of the process. If you are not, don't worry, just use the iron out product if you get more deposits that annoy you.
. That is excellent stuff.
