What causes clothing to fade even if your very careful with them?

i have many favourite dark t shirts that ive treated with great care, washing them on a cold woolen wash everytime, then hanging them somewhere in my flat to dry, mainly on clothes hangers....but already, im noticing at the neck region, around the collar area of the t shirts, they are starting to fade.....and ive... show more i have many favourite dark t shirts that ive treated with great care, washing them on a cold woolen wash everytime, then hanging them somewhere in my flat to dry, mainly on clothes hangers....but already, im noticing at the neck region, around the collar area of the t shirts, they are starting to fade.....and ive not had the t shirts that long?

they are cotton t shirts too.

what could it be? the washing machine itself? something in the water in my area?


i live in north west uk, can anybody help or enlighten me?
Update: thanks texperson, i do get very oily, i have oily skin.
Update 2: thanks jake, i forgot to say i use woolite washing liquid and woolite for dark colours too.
Update 3: many thanks to; - Texperson, jake, michael.
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