You beat me to it guppy! LOL, yeah, I agree, you are most likely dealing with "Hole in the head disease" also known as Hexamita or Octomitus. The holes start off as "pin-holes" but do get bigger, and can spead pretty quickly if not treated early. This disease mainly affects Cichlids, particularly Oscars and Discus', but can also affect Gouramies, and has the potential to affect many others. The disease is linked with the protozoan parasite Hexamita (hense the name). It can often be present in low numbers of fish, with no adverse symptoms, but a severe infection typically doesn't occur unless other factors like poor water quality, and a lacking diet play a role. In the advanced stages, your fish may stop eating, and become hollow-bellied. This can further complicate recovery, as without proper nutrients, the bodily functions weaken, and can eventually cease all together, Including the immune system, therefore allowing the disease to progress at a rapid speed. As far as treatments go, I agree with guppy on isolating the infected fish(es), and treating with Metronidazole. You can also use Dimetridazole (5mg/litre). In some places, you can only get these with a vet perscription, however, in other places, you can find them online, or in any large aquatic store. You may want to repeat the treatment a few days apart, and like guppy said, continue to do 20-30% water changes, as virtually all meds lower water quality (something you can't afford right now). You also have the option of using medicated food, but if your fish are not eating well, this will be a waste of time, and stress.
I do not believe this diesease is irreversable if treated early enough. If ignored, or mis-diagnosed though, it can become fatal, and therefore "irreversable" lol, but you know whats going on, and you are treating it, so fatalities should not be a worry of yours right now. Just make sure you keep the tank clean, monitor your parameters daily, and watch for any changes good or bad. I also agree to use live earthworms during the treatment. They are rich in nutrients. Good luck.
--EMI
I do not believe this diesease is irreversable if treated early enough. If ignored, or mis-diagnosed though, it can become fatal, and therefore "irreversable" lol, but you know whats going on, and you are treating it, so fatalities should not be a worry of yours right now. Just make sure you keep the tank clean, monitor your parameters daily, and watch for any changes good or bad. I also agree to use live earthworms during the treatment. They are rich in nutrients. Good luck.
--EMI

He only has a few shallow ulcers near his snout / forehead area. I've already did water change as suggest and have added a bit of salt. All carbon is now removed.