Neon tetra disease?

So I was looking at my tank today, and its due for its next water change tomorrow. When we moved we replaced our pleco and added two tiny corys. Thats all the changes we made. But now one of our tetras has a bleached out looking spot in its tail! A quick google search and the only thing I found was neon tetra disease. Anyone have any experience with this and know how on earth my poor fishy could have gotten it? Can it just be carried on fish? And lastly, is my whole tank screwed?????

isolate the fish for starters, since it clearly bothers you, if it doesnt improve soon id simply euthanize the fish. just my advice, you could also add some melafix (tea leaf extract that helps promote healing) or extra stress coat. i wouldnt go to far down the road of clearing up a possible disease in the tank, it can lead to worse problems in the long run. GL w/ it

We pulled that guy.... but now my betta has white stringy poop. And the new pleco died. Something got into my tank and now I am worried. ugh!!!

Then its not Neon Tetra Disease... sounds more like parasite?

Yeah thats what i am thinking. I wonder if the pleco died and maybe betta ate at him... We are treating with Jungle Internal Parasite guard.