have you finished your treatment of parasite clear?
also is your other endli having fin rot or other infection? if it is, i'd switch to tetracycline and salt. if you don't see signs of fin rot or other bacterial infection, then it's not necessary to use antibiotics at this point. just make sure you do frequent water change to keep the water good, and add salt.
if you're really worried and wanted to treat with tetracycline just in case (e.g. if it acts or looks like something is developing, but it's not obvious yet), you could do that too. i normally don't suggest this since overuse of antibiotics is a real concern (not in terms of harming the fish, but in terms of bacterial resistance). But you're the one who knows the condition of your fish the best, i thought i'd mention this as an option, in case it's warranted. If you are to do it, make sure you complete the full course of treatment (for me, each treatment lasts at least a week, and i repeat if necessary, with a water change in between).