Sick fish?

[johnnyberotten]

I purcased two, one inch discus a month ago. They were added to a tank with 5 other 3.5 inch discus. One of the new ones never joined the group or fed with them. She is getting more and more withdrawn to the point it just sits in the top corner of the tank. Nobody pics on her, she's just left alone. Also hasn't grown, the other is twice her size not.
Question: should I remove her from the tank?
Is there a medication I could try?
She looks healthy otherwise, its never been de-wormed.

My water is prestine.

Any suggestion?
Thanks

[RogueDiscus]

Hi John,
It's hard to say with fish that small. Does the fish eat at all? What are you feeding? Where did you get the fish?