Looks like Duck lips.. Many people use Metrodinazole or Maracyn, but the success rate is very very low. I'm not 100% sure if its Duck lips, but if it is, you might as well say your last goodbyes to your fish now.
Doing a large water change and adding salt won't hurt.
EDIT: After some searching, treating for Gram + and - bacteria MIGHT work, but still the chance is slim. Whats the temperature that your GT is in? Drop it to around 75 degrees to slow the reproduction rate of the bacteria. I did read something about its some type of bacteria that is resistant to medication. Best of luck to ya.