If everything is green and doing well, you shouldn't need to supplement. If not, it may help to figure out what it is they need. This link may be helpful for that:
Deficiency list for plants.
The anubias (and other plants with roots NOT buried in the substrate, like java fern and java moss) are water column feeders, and can be supplemented with a liquid fertilizer like Seachem's Flourish. If the plants' roots are in the substrate, they may do better with a root tab (like Seachem's Flourish Tabs). I've been using both of those (I've got anubias, java fern, java moss, crypts, elodea, wisteria, ludwigia...) and have found they're pretty good - the plants got a lot greener and started to grow faster.
There's also Flourish Excel, which adds carbon for the plants for tanks that don't have CO2 injection. If you've got a low-tech tank that probably won't be necessary (or so I've read...)