Is this mold or some other damage?

Tried mold killer and wiping it but nothing seems to work.
I am not sure it's even mold, as it doesn't look as spore-y if that makes sense, but I am really no expert.

Any advice or hint is appreciated!

-live on top floor
-aircon runs 24/7 on dry mode
-have dehumidifier in room
-aircon did blast on the wall affected (just dirty air? Lol)

https://imgur.com/a/EyFp4Zw