Fin Rot being the closest description I've got in my arsenal. Besides the tail, the lower body fins are also fraying.@Jay Hemdal
I do not see 'fin rot' per se? When I have seen aggression - its often not constant - and if unless you're watching closely 24/7, it can be easy to miss
It definitely had something going on, kana cleared it well up, I watched the tail regrow day by day.
I'm not saying it ISN'T aggression, but the problem going away immediately after treatment, then coming back makes me wonder.