good morning Newbeefishlover..
I usually watch the aggression for injuries or prolonged stress. In those cases, I would immediatly look for another tank for the aggressor. If that is not an option, then I would take it back and hope for a refund or an exchange of fish. I find that the whole tanks health is not worth the aggression of one fish IMO.
As far as what was suggested about the larger tank, your tank may very well be over stocked and can accelerate the aggression. As far as maybe making more hiding spaces available for the stressed fish to be able to hide in may be an option if getting another tank is not.
Good luck with your fish and tank!

~ kate