Kha'Zix's passive always showing up

I recently played a game as Kha'Zix (if that somehow helps i was running Mecha skin) and there was one enemy that would always get the isolated visual effect (even when close to other champions/turrets/minions) I absolutely can't tell if something triggered it or if it was always that way since i truly noticed at around 7 mins in.

They only got the visual effect, without the bonus damage or bonus slow with evolved w.

Also it only happened in that one game even though I played a bunch of Kha games so I can't "Follow up the description of the bug with numbered step-by-step instructions on how to reproduce the issue."