iron mold vs discolouration

iron mold and discolouration both are nouns.

Word	Noun	Adjective	Verb	Adverb
iron mold	Yes	No	No	No
discolouration	Yes	No	No	No

As nouns, discolouration is a hypernym of iron mold; that is, discolouration is a word with a broader meaning than iron mold:

Other hypernyms of iron mold include discoloration, stain.

iron mold (noun)	discolouration (noun)
a spot caused the staining with rust or ink	the act of changing the natural color of something by making it duller or dingier or unnatural or faded
	a soiled or discolored appearance