Help! My Gold Sev in Critical Condition !!

I bought a small gold sev 2 weeks ago...he was eating good..but yesterday i saw white spots all over his body...so i bought Malachite Green F and Rock salt...and started the treatment..BUT WHILE CHANGING WATER...I SAW THE GOLD SEV DORSAL,PECTORAL FINES HAVING RED LINES AND RED SPOT...A DARK RED SPOT IN PROXIMITY TO GILLS...
IDK WHAT TO DO...PLSSSSS HELP!!

MY TANK (28 GALLON):
5 CHICHLIDS
1 GOLD SEV
1 GREEN CHROMIDE
CHANGED 75% WATER SO AMMONIA IS 0
AND CURRENTLY THEY ARE IN ROCK SALT AND MALACHITE GREEN MEDICATION
PLS CHECK THE PHOTOS!!

Something like this also nose too red!

Your 28 gallon tank is too small for just one of those 5 cichlids you are currently keeping. It is no wonder you are struggling. I would also stick to either African cichlids or South American, and I would not mix them.

Even if this mess in your tank is resolved, you will continue to struggle with overpopulation, fish stress, unstable water parameters, and fish illness.

I feel so bad for your fish and for your struggle in this situation. Perhaps you should buy a 200 gallon tank to give your fish a suitable home if they can be brought back to health and keep this 28 gallon as a hospital tank. Then you could start to resolve this problem. No sense of resolving a problem that leaves your poor fish in the same abhorrent situation that will perpetuate the vicious circle. I really wish I could provide you with hope and a better solution to help get you out of this situation. You will have difficulty finding someone to take sick fish meanwhile If you decide to just start over from scratch.

MUCH more research needs to be done on your part before you start stocking your aquarium.