Your fish do not need salt, especially not aquarium salt which will not create brackish conditions. For that you need marine salt.
I agree that your pH is fine. Most likely they starved unless your tank has a lot of algae or is heavily planted and can supply a lot of decaying plant matter.
I agree that your pH is fine. Most likely they starved unless your tank has a lot of algae or is heavily planted and can supply a lot of decaying plant matter.