What did you feed that might have lead to temporary white poo? Blood worms, tubifex? They have a chitin outer layer that fish don't digest easily...If it's just an occasional issue I wouldn't worry yet. You might try some veggie type foods & see how that poops out...OK, to graphic before my dinner...
Aquarium salt is not a treatment for any problem I know of (but table salt may be). Bacteria issues require antibiotics, parasites need wormers of any of a few kinds...We need more info over a couple days...