The following graphic an NCT fan made shows at least 6 different hair colors the idol has donned since his debut about 8 months ago. You can clearly see the hair becoming less and less healthy looking with each change of color and style.
And as if to prove his fans' concerns to be correct, Mark was recently seen with this hair.
Fans suspect that an SM stylist bleached his hair yet again to get him ready for the early 2017 comeback. People who attend the same school as Mark say that his hair is in such bad shape that the idol wears always wears a hat.
In the picture below, on the left, is Mark from 8 months ago, and on the right, is Mark recently.
What do yo guys think about Mark's transformation?