Illness/Sickness: I need some help, Axolotl Sick/Fungus?

I woke up yesterday to find one of my female axolotls missing all the color and 'fluff' off of her left side gills. There was chunks hanging from them and it looked like something had been eating on her. I put a few feeder fish in the tank a week prior, and her appetite has been healthy. I removed all the fish that was in there thinking they were the culprit, and today noticed that it looks more like white cotton pieces all over her chewed up gills and it has spread to another gill on the right side. I have three pictures I took of her. I looked it up online and all I am coming up with is a fungal infection? I wanted to ask all of you what you guys think and what you suggest I do. She is in the tank with one other axolotl and so far the other one seems perfectly healthy. The sick ones gills look so terrible and with the seeming spread of whatever it is, I'm super concerned. Any help would be appreciated!

Definitely looks like someone took a bite off her. It's hard to tell from the photos if there is fungus, or if it's just deteriorating flesh. Fungus presents as cottonball-like growth, wisps. Fungal infections usually respond well to refrigeration and salt baths.

How big is your tank? And how warm? Do you test your water quality? How often do you do water changes?

Feeder fish aren't generally recommended for this exact reason. Earthworms are a much more acceptable and nutritious food for axolotls.

The tank is a 30 gallon and the two of them are the only things in it. I give them a mixture of feeder fish and also earthworms and they eat like horses, so they have never shunned away from a meal. Even now the injured/sick female is still eating regularly and showing no signs of being sick. The tank averages at 66* F.
I cant tell either if its a fungus or the fish just picked on her really bad. All the fish have been removed now and it doesn't seem to be getting any worse or spreading, and the other female has no gill damage. So maybe its not a fungus? What do you suggest? Start a salt bath treatment and fridge for her injuries even if it isn't fungus?
I do 25% water change once a week but I haven't checked the water quality lately. I need to get a water test kit immediately I know.

If it doesn't appear to be spreading, I would wait and observe. Salt baths can be quite irritating to the skin, especially the gills. So if it's just the damaged flesh flaking off, there's no need to put her through salt baths.

However, fridging could be beneficial. It's not harmful, and can be done for a few days.