Loss of pigmentation can be due to a variety of causes including aging, allergies (perhaps latent effects in your case), and seasonal changes. This is not life threatening and need only be of concern if in the sun a lot. In that case, use sunscreens.
It is also unlikely that they are in need of extra vitamins. However, we do recommend rotating the diet for optimal health. In addition to the Epigen™, consider the Anergen™
, the TNT™
s, and the new Fundamentals™
diet, which all are helpful for dogs with allergies. If you wish to use supplements, consider these: AddLife™