If it was a mild bacteria infection your fish has, yes they can show symptoms for months.
I still worried as it could be both parasite, bacterial.
I need to read the whole post again. As it beginning to get abit confusing.
Furanol 2 by JBL. Will wipe the good bacteria out in your filter.
Antibiotic can only be prescribed by a doctor, or vet, in the UK. Will also wipe the good bacteria out in your filter.