Dawn is still convinced this originally was an injury
However, it is obvious there is surely an infection raging here. I have been sitting here with my husband looking through these photos and trying to decide what will be the safest and most effective treatment for you. I'm going to suggest tetracycline for this situation, and let me explain why. For starters, the Maricyn 1 & 2 are quite harsh on the biological cycle (one is worse than the other, but together still quite harsh) and at the same time Maricyn is a milder medication. It would require 2 medications to cover for broad spectrum treatment (gram positive and gram negative bacteria).
Tetracycline is broad spectrum, safe for African cichlids, more potent than Maricyn, and not as harsh on the biological cycle in the tank... and it will also help avoid fungal infection from setting in. There are other options, but tetracycline is going to be probably the best at this point. I am taking into consideration how quickly this infection has spread and to what degree. That tells me it is an aggressive strain of bacteria, fast progressing and in need of a strong enough treatment to get rid of it quickly. If its spreading that fast we don't really have much time to play trial and error with meds, working from mildest up to strongest to see what works.
At this point, if none of the other fish in the tank appear infected, I am going to suggest treating only the infected fish. I'm wondering how long since this problem with the other fish happened? I was unaware that there was another issue in this tank prior to this... and that makes a whole world of difference in diagnosis and treatment. I agree that breaking the entire main tank down is probably not the best idea. If the other fish are showing some kind of symptoms that follow suit with the first issue and then this one, then I would say go ahead and treat the main tank at the same time as the QT with this fish. I think this fish should stay in QT for a couple of wks to allow it time to heal before having to face the aggression of its tank mates again.
My advice to you in pm about needing much more decoration/rock work in that tank still stands, and this should be done before moving this fish back into the main tank. During treatment remove all carbon from filter(s) and follow directions on the medication instructions. The medication may stain the water a yellow color during the course of treatment, this is normal so don't be alarmed. The color will come out at the end of treatment when you do water changes and put carbon back into your filter(s). I have never known tetracycline to cause permanent staining like some other meds will.
Best of luck to you! If you need more help or more clarity for my suggestions, please just let me know.