Cichlid dying from stress?

[guychiclid]

Hey, I did my weekly 30% water change afterwards I added seachem clarity and sera toxivec. After 3 hours of changing the water I noticed one of my acie's dying at the bottom of the tank. This cichlid was lately (this past week and a half) bullied by two of my other cichlids, but I assumed it was just cichlids being cichlids. My dead cichlid was hiding behind rocks for the past few days. And today he died.

Could it be stress?

Or is it from wc? Although it's been the same water I've been using since day one.

Please help i don't want my other cichlids dying.

P.s he was the biggest cichlid in the aquarium about 3.5"

 

[SonicsDC25]

How were his physical conditions when he was being bullied (fins, mouth, ect)? Aside from sitting at the bottom, were there any other symptoms?

 

[guychiclid]

His fins were a little damaged but nothing critical cause else I would have moved him.

 

[FrankoQ]

I always move a beaten fish to the hospital tank. My thoughts are that the fish is stressed and physically damaged. (even if it seems fine). In the hospital tank, I put aquarium salt or Melafix.