I bought this little veiltail female from Petco today, hoping to add her to my female Betta sorority, but I notice she's not doing very well since I brought her home. She's been isolated from the main tank, and is very lethargic and just sits at the top. I got her because she's a tiny little thing with unimpressive fins and knew there probably wouldn't be anybody else interested in her. I was in Petco a week before and she was there. I feel bad for her, I'd like to make her healthy again but I'm not sure what's wrong with her in the first place. She doesn't seem to have any outer appearances of diseases or parasites. I currently have her in a small container with fresh water and some salt.
Any ideas/tips on how to hopefully make her better? Here's the best picture I could take of her, my iphone isn't very good at taking photos of fish.