Need some inputs,

I have a 2018 Perodua Axia in White and was involved in an accident around 1 year ago which required me to replace my hatchback bootdoor. Fast forward about a year the paint on the bootdoor is turning yellowish while the rest of my car (the parts which are all OLDER) is actually still white, wth? I've been told that the car which was made in Rawang have been treated with some sort of chemical while the new bootdoor at the body/paint shop was not thus it turned yellowish faster? But accident replacement should be Perodua original parts is it not?

Any advise is appreciated.