For recently-acquired newts, particularly ones that come from pet stores, there is a two-fold very high risk of disease during the first month or two: first, they have been traumatized by the whole import/retail procedure, in which they are put under stress and exposed to the germs of other animals. And second, they are usually put into a new tank, which can often suffer "new tank syndrome" (see FAQ, link in my sig).
There are non-disease reasons that a newt might have a white spot, but since they are recent newts, you need to be vigilant for signs of disease. We still need a better description.
