The activated carbon (different than charcoal) should remove the staining in the water as well as the beneficial humic acids and tannins, but it depends on the quality of the carbon. It differs from charcoal because it has been high temperature treated to open to open up billions of tiny 'pores' that help it absorb chemicals from the water (or air).
Personally if I need to remove the peat staining from water I use a product called Bio Chem Zorb which clears it up very quickly...
Regarding the black water extract, one of thebest Discus dealers in Dublin always recommends adding blackwater extract rather than peat, then again which is more expensive to buy......
Ken