Given the lack of improvement, might try a couple of things empirically as your expected outcome at this point without improvement is terminal.
1. Would try a clean out with epsom salt first
2. Next try orange peel which can stimulate appetite. http://forum.simplydiscus.com/showth...ht=orange+peel
(either 1 or 2 could be done first as they are both essentially risk free interventions)
3. If that fails, my next step would be a course of metronidazole.
4. Lastly would consider treating for parasitic worms but that seems very unlikely given no other fish are showing symptoms and usually they suffer from wt loss more than anorexia.
As an aside why do you rely on AC to remove chlorine/chloramine vs using a dechlor like seachem safe?