What are your dog's water and food bowls made of? Plastic can cause a pink spotting of the nose:
Physical ailments and medical conditions may also cause a dog’s nose to fade from black to pink. Sometimes, the dog will lose pigment due to an illness or trauma, and then recover the pigment once healed. If your dog’s nose is scraped or suffers abrasion, it will usually turn pink as it heals, then to black once the scabs are gone. Contactdermatitis can also cause loss of pigmentation in the nose. Certain dogs are sensitive to plastics in food dishes, and the continual irritation will cause the nose to turn pink; the lips will also become inflamed. Switching to stainless steel food and water bowls will eliminate the possibility that your dog is suffering from contact dermatitis.
(Why Is My Dog's Nose Turning Pink?)