Dens don't like a lot of nitrogen, so the 30-10-10 will not be suitable. The bloom formula 6-30-30 would be better, year round. Your den is a Yamamoto type, and they don't need the severe drying out like the regular nobiles do. I stop fertilizing mine at the end of August to allow the canes to mature. In November I start to dry it out by giving it less and less water. Then I leave it go completely dry until Christmas, when I resume watering again. However, I don't drown the plant, I give it what I call "baby sips". The leaves are deciduous, but they don't drop every year, perhaps every other year. Mine just finished blooming.