It is a parasite. I've seen this before with Rams. It was extremely contagious and spread once the parasites broke the skin surface. I would suggest a couple doses of Prazi Pro or an edible anti-parasitic laced food (MetroPlex http://www.seachem.com/metroplex.php).
Good luck with the treatment.
PS: If you are not too attached to the fish and no other fish have the same symptoms, culling may be the safest and easiest option.
It is a type of internal parasitic worm. I never got a correct ID. My friend eventually euthanized his infected stock as it became extremely contagious. It initially started with his tank raised/bred Rams (several different varieties that were not wild-caught). It also spread to his Cardinal tetras.
I'm sorry to hear that. It sounded difficult to treat, but isn't Paraguard used for external parasites? Prazi and metro are for internal. Although, seeing how fast he went, it might not have made a difference.