Please help me identify issue with Koi :(

[Reccy10]

I have a koi, which I can see is sick, but I am really unsure what's wrong.

I can see no outward signs of disease. I purchased her about 4 weeks ago and she seemed fine.

She had a bit of an issue a couple of days after she was added to the pond, I don't know how she did it, but she managed to get herself on top of the pond net, luckily she was heavy enough to weigh the net down so she had enough water to survive until we spotted her and got her back in the water (don't think she'd have been out too long). We have since removed the net and added wire around the pond instead to protect from herons. She had some abrasions on her body and a bit of sunburn but after adding a bit of pond salt to help her recover she seemed to recover very well. I also did a fungus and parasite 5 day treatment just in case any took hold while she was recovering.

However about a week or so ago she started sitting near the top of the water, I would say breathing heavily but not gasping, but today she is swimming around the surface of the pond listlessly, banging into things before reversing.

She is not being bullied or anything, in fact the rest of the koi seem very concerned for her and are swimming with her and seemingly checking up on her gently.

PO4 is 2mg/l
NH3 0mg/l
N02 0mg/l
PH 7.5
N03 20mg/l

Pond is partially shaded with plants.

I've added a picture of her below plus the other fish. None of the others seem to be having any issues.

Screenshot 2025-09-07 at 13.39.02.jpgScreenshot 2025-09-07 at 13.38.51.jpgScreenshot 2025-09-07 at 13.38.43.jpg

[Djstiles999]

Could be lack of oxygen or parasites, I’d add air and do a scrape as a start

[Alburglar]

You need to scrape for parasites. There is no generic treatment that treats all of them.