1. Keep your water really clean (make sure ammonia is kept at 0 or close as possible, ALL the time, and use a good brand of water dechlorinator like Prime) and stable (keep his temp even at 78F, don't add unnecessary stuff like pH adjusters, aq salt and the like..)
2. High quality, high protein food will help with regrowth. Live food is great additional nutrition.
3. Add a little Stress Coat to the water ( - I don't use it as a conditioner all the time, but as an occasional additive for new/recovering fish).
4. Add some ketapang (Indian Almond) leaf. One new leaf each couple of weeks will darken the water/reduce stress and also add some great antifungal/antimicrobial stuff to the tank.