Yellow Fin damsels

[Pop]

So I got two yellow fin damsels in my tank and I trusted the guy who gave me the fish. He gave me a healthy one and the other was slight faded. I didn’t bat an eye to that but after a few weeks of having those two. The healthy one was bullying the weak one so much I had to separate them.
What should I do ? The fish seems so weak already and I don’t know what to do..

 

[Old Fritz]

Would you be able to return it? Damsels in general (excluding a few species) are mean little guys. He'll probably pick on any other fish you want to put in the tank.

 

[Pop]

Would you be able to return it? Damsels in general (excluding a few species) are mean little guys. He'll probably pick on any other fish you want to put in the tank.

I already have other fish before them so. They are the last fish in my tank. And the shop I got it from don’t allow returns..