Yeah I would dose Seachem Flourish and Excel. For Iron and Potash, you can get a bottle of API Leaf Zone as well. The root tabs wouldn't be that necessary since I don't think Java Fern or the Anubias are heavy root feeders. If you add plants such as Swords and Crypts, then yes, root tabs are recommended. The directions are on the bottles, but yes, you just add to the water.
If the brown is rubbing off, it might be diatoms... that will subside on it's own and is usually found in new aquarium setups. Snails such as Nerites, or even Otos can be added to help control algae (including diatoms, which is not actually an algae). Otherwise, continue rubbing it off during your normal PWC routine.