Try adding vitamin B complex vitamins to the water, and make a paste using a little water, vitimins and some flake food, buy capsules, they don't have coatings, or need to be crushed. I have had pretty good results using Furan 2, maracin 2 is ok and not at all like maracin, maracin is not good for much other than cloudy eyes, killing red algae in saltwater, and messing with biological filters. I've never used melafix, the jungle fizzies are ok, but a simple tablet or capsule would have been beter, why fizzies? Salt is a good preventative, about a half teaspoon per gallon for gold fish helps them healthy.

It sounds like he has bacterial fin rot and those meds are not strong enough. Keep water pristine, can increase salt slowly over time to several teaspoons per gallon.. may need antibiotics. Its late now and too tire to dig up all links, but do search for fin rot. hurry as if it goes into fish painful and not good going forward. wouldnt worry so much about feeding right now, but if eating adding vitamins as suggested will help with immune system.

Could be by now several things. (fungus and bacteria, often coexist) I have (as others have mentioned) better use of garlic in food and stop treating flex bacteria) see albino cory post (read down)

At this time would spot treat (ie take out gently and treat with something directly. Then use salt dip for reduction of osmostic stress and healing so on then return to hopsital with salt... salt in hosp in built up over time (they can handle more then you think if done slowly , add water to salt mix first then dribble slow over time)one teaspoon gallon a day up to (my betta is at three and fine) that and possibly more if warranted.

dip is shorter but stronger drible in slowly watch for stress...

I used mecurachome directly (I diluted a bit with water and used cotton swab, careful not to rub just dot)

THis links provides ideas and has photos.

http://www.fishdeals.com/fish_diseases/fin_rot/

Best Sherry

here are some links best of luck slm

http://www.kokosgoldfish.com/disease.html

Fin rot (phots of treatment)

http://www.fishdoc.net/disease/finrot.htm

In more advanced cases it may be necessary to trim the affected fin and remove the necrotic tissue. This has to be done when the fish is sedated. It is important to use sterile scissors and treat the clean edge with an antiseptic such as povodine-iodine. This procedure does carry with it a risk of secondary infection and it is important that the fish is returned to optimum conditions and its progress closely monitored for the next week or so.

If the fin rot has advanced the full length of the fin and is threatening the body, this procedure would need to be accompanied by a course of suitable antibiotics.

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This is betta talk but has good photos and description treatment

http://www.bettatalk.com/betta_diseases.htm