Everything in your description REALLY sounds like columnaris (aka flexibacter) especially with it growing on one of their lips. This was what wilder was talking about in the first post. There are several different ways this disease can present itself. This disease is often called fungus because it can look like fungus, it can be called saddleback because it will make the fish look like it was wearing a saddle, mouth fungus (self explanitory), and it can cause ulcers. Just because it looks different from what your tetra had does not rule out columnaris.
Adding salt can help with this disease, so that is a good thing. You will need to treat it with an antibiotic. My personal favorite is Kanacyn (aka kanamycin, k-mycin). You can also use a combination of Maracyn and maracyn 2. Tetracycline is also an option, however, it can harm the biological filter.
Best of luck!