The problem with this is that while it may not be visible and hence it appears they are fighting it off, it could well be rampant in their gills and still compromising their health. That said, I and many others have succumbed to such an approach after failing to sufficiently QT and not wanting to start from scratch. If you go that route, I think it is helpful to add a good UV sterilizer to your system if you don't already have one (can't recall) as this will help reduce some of the circulating load somewhat - not 100% effective but still better than nothing (make sure to scale this properly though). Tough call for sure but a full scale QT reboot can be done if you are patient and very detail oriented. Good luck!