What are your water parameters? The brown stuff you are seeing is most likely brown algae or just dead plant material. Brown algae can be caused by high nitrates and insufficient lighting. With 20 cichlids in a 30 gallon you are over stocked in my opinion. What are your water changes like? What kinda lighting do you have? Anacharis get most of their nutrients through their leaves. A good liquid fertilizers will do wonders for this plant. Also this plant is medium to high light requirements.
Anacharis plants have never been a favorite of mine. If this was a different plant I would say you could wipe the brown algae off, but i doubt you could do this with the anacharis.