The coach maintenance depot doesn't do anything about the exterior paint fading. External painting of the coaches is done at designated coach workshops once every 18 months. If the workshops do not use the prescribed paints (Epoxy PU) then coaches will have this faded appearance. This happens with quite a few rakes as these workshops tend to do an incomplete job due to time constraints. The train is just unlucky that it got these improperly painted coaches.
Internal maintenance though, is definitely the responsibility of the passengers and the coach maintenance depot.