I don't have as much experience as some others that have posted but I've gotten several fish to include a Bellus with Lymphocystis which is a virus. IMO yours looks a lot like it, white and fuzzy like cauliflower. Maybe that's what it is and why it hasn't responded to meds
I think you may be right.
I have read that it is possible for lympho to open the fish to infection, and I think that must be what happened. Either there was a wound that got infected and simultaneously broke out in lympho, or the site of a lympho episode got infected. That is possible, right?
The site of the original infection appears to have either healed, or at least gotten much better. That side of the fish was swollen, and you could clearly see an inflamed area. Somewhere along the line, I also started a small UV light, figuring it could not hurt at this point. I think that, combined with the meds, helped either kick or significantly roll back the infection. The fish has also never stopped eating. That's the good news.
The bad news is that the poor little gal has lympho run rampant. The swelling at the site of that original infection has gone away, but that part of the fish is covered in lympho. And it has slowly spread to the fins. I suspect that, even though I was doing 25% water changes every day with the NGP, and feeding LRS reef frenzy spiked with vitamins and blackworms too, the immune system has not been able to keep up with the infection AND the lympho.
I've been watching the lympho spread, knowing that it should not be as serious as the infection, and waiting until I could declare the infection cleared before I started to address the water quality issue. I stopped all the meds about 2 days ago, did 50% water change, and have been running carbon. The water still has a tint of the lovely green that NGP induces, but I will keep up with the water changes until it is nice and clear. Hopefully with the infection cleared, the fish can overcome the lympho. I will try to get some pictures as soon as the water is completely cleared of the NGP green tint.
The NGP really did seem to move things along - both in reducing the infection, but also in accelerating the spread of lympho. Is that possible?