If you are convinced you did everything you could for IPs with stand alone meds. then treat with Kanamycin (Seachem Kanaplex) in combination with API General Cure (Metro/Prazi). If you can't find Kanaplex another option would be to use Neomycin available as Seachem Neoplex but do not combine this with other meds. Food can be soaked in some Neomycin and fed via syringe into the fishes mouth if it isn't eating. I think the Kana/metro combination is your best option.