Your first coin is discolorization. Or toning. that happens to raw metal just sitting around exposed to air over time. Remember coins are not painted to protect the surface, so anything can happen to the metal when exposed to the elements from just air, to being on and in the ground.
The 2005 nickel as well as well as the rest of this series do tone this color! The reason they do is the wash that was used on the platchets . It not due to any "other exposure"... the entire series including the proof strikes do tone this color.....I have rolls of them at one time all turned this golden tone. Including the mint proof set that had a mock version of the peace medal.