From what I read so far on Allkpop, I personally think that maybe the bullied person perceived it as bullying while the other members did not.
I mean, just thinking about it, if a person is somehow feeling "outcasted" from a group, then it would be plausible that because they feel singled out, they might incorrectly perceive everyone is against them, and perceive actions as worse than they are, or perceive deliberate bullying intentions from actions where there were none.
I just think that it's just like a situation in a friend group where one person feels awkward or doesn't fit in for some reason, then people don't know how to act around that person, and that person feels outcasted from the group, and that creates misunderstandings.
This is what a bully usual thinks though.