Harlequin Rasbora in bad shape

[anitstuk]

Hello everyone, haven't used the forum in a long time but I need some help. I've left my aquarium to my dad to manage for about 2 months now and I've checked in every now and again to see how its going. Today when I checked, one my my Harlequin Rasboras's looks like it's suffering from popeye and it's also missing a tailfin. It's staying with the group but struggling to swim. Any ideas on how to help it get back to health?

[Colu]

What are your water parameters ammonia nitrite nitrate pH KH just case something off looking at the picture I would quarantine and treat with kanaplex and aquarium salt 1 table spoon for 2 gallons the salt will help reduce fluid buildup in the eye could a fin rot or an injury to the tail it could  be bacterial that's why I recommended kanaplex it's a broad spectrum antibiotic treatment @anitstuk