Achilles tang, never had this problem before

I bought an achilles tang just about 3 weeks ago now.  The first week went well; at least it was eating right out of the bag when it arived.  The second week, it began eating any food i threw in the tank.  The fins were completely out/strutting around the Q-tank.  I had been feeding this fish 3-8 times per day.  Feedings included red, purple, brown, green nori sheets and soaked in either Selcon, Zoecon, Vita Chem, or Kent Marine-C.  I also feed Cyclopeze and home made fish food once a day. 
I bought the fish through the diver's den of Liveaquaria. And had felt very confident that this fish would be going into the display tank very soon.  I had more troubles with a powder blue than i had with this achilles at this point.
No signs of illness untill a couple days ago.  There were a few white spots on the body and a funny swollen area on the dorsal fin.  So I began treating for parasites with ICH-X.  The next day, I see that the left side of the fish has a damaged area just behind the pectoral fin.  I had done a 50% water change and retreated for the parasites the day before.  The next day, the wounded area apears like a large burn or ulcer'ed area.  The skin and scales appeared to be receding and exposing muscle.  The achilles keept going over to the only other fish in the tank, a yellow sailfin goby, and wanting the goby to clean it's wound; but the goby would have nothing to do with the achilles.  BTW, the goby is doing very well.
Today, the injured area is larger.  And the fish has stopped eating.  The breathing rate has dramatically increased.   I am guessing this fish is having troubles retaining water in it's body.  Luckily it had been eating supplimented food like a pig for the last two weeks.
I am thinking i will attempt some anti biotics.  continue the water changes.  Take it lightly on the parasite treatment until improvement.  and I am open to suggestions.
I am not even sure how this happened to the fish.  Weather or not it is a burn from the heater, or a bad injury from something unknown to me.  i will try to get a couple pics up, as soon as i figure it out.

 

The fish died the night after i posted this. I have a bunch of photos of the fish as the ailment developed, until death. I sent pictures off to liveaquaria, they responded that it appeared to be an internal bacterial infection.

LiveAquaria:Thank you for your email. After reviewing the picture provided, our best guess is that it was infected with an internal bacterial infection, Mycobacteriosis. The first sign of this is sunkeness just behind the pectoral fins and in the stomach. White nodules, scale loss, and skin lesions are also common symptoms. Unfortunately, there is not an effective treatment known for this disease. At this time, we would recommend sterilizing your quarantine aquarium, to prevent future infections. Again, this is not a definite diagnosis, as we are only able to give our best judgment, based on the pictures.

I can not say enough about LA. They bent over backwards, crediting me for the fish, contacting me via phone that another achilles is coming available, and the shipping of another fish.

I will try to post pictures again. I had troubles uploading last time.

I have the fish in the freezer yet. Anyone know a taximermist that would like to play around with a little saltwater tang for real cheap!???? /DesktopModules/ActiveForums/themes/_default//emoticons/smile.gif I bet i have a dead piece of coral or rock it could be glued to! (now i sound like i kill everything!)

 

Two and a halfweeks
Dead
Second day sick
first day

 

I got a second achilles this last thursday. This new one is twice the size, and has adult coloration (about 5 3/4"). It has been a picky eater too. ONLY red seaweed that i rubberband to rubble. Won't touch the other colors, and does not seem to pick supplimented algea either. However, this fish seems to be picking up momentum in his eating habbits.  I am putting fresh seaweed in the tank 2 to 3 times a day, and still only the red is being eaten.
    This time i decided that i would just throw the fish in the display tank, right off the get-go. I did give it a bath in ich-X just before transfering it from the bucket to the display tank.  I also had to put a divider in the tank to keep the powder blue from beating on him; and get this fish's confidence back up.  SO far, so good!

 

andythereefguy - i wouldn't mind it one bit if you wanted to do a necropsy on the fish. It is still in my freezer. I live in Ames, but will be in the cedar falls/waterloo area in a few days.