Danio Disease, head tilted up, curved spine, red sore

[JuliandAaron]

tank stats: 

65 gallon, community tank, heavily planted, canister filter, plus power head for added current. 

ph: 7.5

Nitrates: 10 ppm

Hardness: 300 ppm

Nitrite: 0 ppm

Ammonia: 0 ppm

Kh: 120 ppm

temp: 78 degrees fahrenheit 

We have about 10 orange fin danios and have had them for approximately 2 years. Over the last month or so I noticed ones body shape slowly changing. She swam and ate exactly like the others, and I thought it odd so I did some research but found nothing about it. And time went on. Yesterday I thought I was watching her and realized it was another one of the danios with a similar body distortion. This morning I found her and was shocked! She is completely distorted and has a bulging red sore in her stomach now. I never saw her because she was hiding and not swimming with the others. 

We added aquarium salt to the tank last week at 1 tsp per gallon since I didn’t know what to do yet but knew something was up. (Now my crypts are melting but that’s a topic for another time🙃) But that’s the only medicating we’ve done so far since we didn’t know what we’re were dealing with and salt is a good place to start. 

I caught her out this morning and she is in quarantine but I don’t know what I am dealing with or how to treat it. I suspect she is not one I can save and may euthanize her but I want to try to treat her first.  

But it’s spreading! Now I see 3 female danios with the same shape but she is the worst. None of the male danios look odd. None of the other fish are exhibiting symptoms.(rummy nose tetras, mollies, rasboras, a betta and some cory cats.)
 

I have found nothing helpful on the internet, some people have posted similar issues on other forums but there was no information or resolution offered. 
Have any of you seen this before? If so how did you handle it? 

[Colu]

 I think your deal with neon tetras disease with the symptoms your fish are showing  such as curved / bent spine and body sores it difficult to treat  and highly contagious 

Edited January 17, 2021 by Colu

[Mr_Manifesto]

This could be neon tetra disease,  or it could also be fish tuberculosis,  either way, it is not good!  Treatments are varied, and success is minimal.   IF it is fish tuberculosis, there is risk of human infection as well... so wear gloves!  Most hobbyist recommend euthanasia.  I personally have a hard time doing that, because I feel like everything living thing should at least have a fighting chance.  I would quarantine all those that have symptoms, and try to medicate.  I don't know what medicines are available or what would even work.