anubias are easy to grow. as long as you have some light and fish in the tank they should grow fine. the fish will produce more then enough nutrients for the anubias. as long as you have enough gas exchange to keep your fish from dieing that should be enough for anubias to grow. (if you completly fill your tank with anubias then you may need to start adding fertz but if you only have a few you should not need to add them)
if you want faster growth you can add more light, more co2 and more fertz and that will improve growth rate. if you want an easy way to improve growth you can buy some root tabs (they go buy different names for different companies) but these just add more nutrients to the soil around your plants roots. since anubias are big root feeders this will help them alot. this is not a must but it can help.