Best thing for Mbuna body rot out break?

Well, fist time ever dealing with this issue. My mbuna tank got an annoying sudden case of...well, body, tail, fin rot and whitening. I need something that will treat and save my fish from this. Its a 75g tank, everything I am finding is for like 20g or 40g max and is not cheap...
Help!!

Well, yellow tail Acei seem to be extremely susceptible to body rot. Salt in water, medicated feed and added [FONT=arial, helvetica]Maracyn[/FONT].
Lost all 5 Acei, another 2 seem to have started downhill. All other fish are fine. 20-25g w/c every 3 days. Cycled tank, 7.8pH, tons of hiding spots. The 7 tiny fry are all fine, too. Acei are just weak fish...

Haven't seen that at Petsmart, does Petco have it?

These particular fish are crazy weak...Maybe I should just quit with them for awhile until everyone else is larger and then buy Acei as adults from breeders. Maybe they will be good then.