Yes you should remove your stones and rocks,it can't be a big problem.
NEVER use any bleach or other chemicals to clean things from your tank,it can kill every life in your tank,including the good bacterias!
First take them out and brush them if you want,but with a brush that you never used before for any housecleaning!
But in a tank with Tanganjika-or Malawicichlids should be alge!
When you are afraid for any disseases,then cook your stones in normal boiling water,let them cool of and then put them back.
When possible on the same place because the fish must find back their old territories.
Of course this whole operation will stress your fish,but with sick fishes it is maybe necessary.
A sick fish you must give threatment in a seperate tank if possible.
Don't use chemicals and medicine first,first bring up the temperature to 30 C for lets say 2 days,then make a major waterchange in this tank,and then see what happens.
Maybe it is not bad to add some normal kitchen-salt,one teespoon on 2 gallon of water.
Is the fish is still sick,then you can always use a proper medicine(a lot of times normal kitchen-salt workes very good).
After use medicine you should always use charchoal in your filter because this takes out the medicine very good.
When you do all of this in your communitytank,this will make more problems then it will help you.
So to be finally short,take out everything that needs desinfection(heater and filter to),catch the sick fish out and put him seperate. for treatment.
And finally try to use chemicals and medicines as little as possible.
I hope i helped you out a little bit,lots off succes with your problem,Willy Bijker,Holland.
Willy,Male,Holland,Dwarfs,West-Africa,Central-Amerika,South-America,Tanganjika,Author of articles,Give lectures to.