Angel fish fin rot?

[Redpanda]

Hiya. I am still struggling with my angel fish and giving myself hard time for being useless in trying to help it. My quarantine tank is a total disaster, constantly showing tinges of pink in both nitrites and nitrates, I change 40-50% water once-twice a day, plus dose it with stability. I think I’m poisoning the fish the hole is not getting better and I can’t tell if there is any improvement at all.
I had a feeling quarantine tank is quite risky even though I’ve asked many questions in previous posts, and now struggling with guilt.
I don’t know whether to carry on as it is, try another Treatment- this time antifungal maybe. So far had Esha 2000 and myxazin.

Or just return fish to main tank and forget the quarantine tank completely. I think it wasn’t not enough media in the first place and how it’s not coping with one fish I’m not sure. I don’t think I’m over feeding. Fish eating and pooing as normal.
Ohh so frustrating.

[plankton]

Is the fish getting worse?

[Redpanda]

I think the hole is either stopped spreading or slightly increasing but it hasn’t improved as such unfortunately.
He had tiny white patch near tail too, and that’s bigger I think. From 2mm to maybe to 3 mm diameter .
Just worried about the nitrites more than anything. That it will not be helping.
What would be best antifungal treatment to try ?

[plankton]

I don't know what the best is, probably whatever the Waterlife is - Protozin?

[Redpanda]

Moved him back to main tank. He’s super happy and feeling better, rather than sitting in poisonous water the ulcer is not great though but he had 6 days treatment so will give it a break and see if being in good water will help him.
Thanks

[plankton]

I'd finish cycling the q-tank, just in case.
Hope he does well now.