It is better to use liquid fertilizers. Spray fertilizer to wet all the roots and leaves. Interval of fertilizing is two to three weeks. Flower of the Guzmania plant is remain for at least three months. New germs arise from the stem when the flower start to fade out. You can keep those new plants to make a bush or remove those from the mother plant and re-plant to get new plants. But new germs must grow one third of the height of the mother plant before separate.
There is a low possibility of invading diseases to Guzmania plants. Flowers may damage by snails like plant eating creatures. Use an insecticide if the damage is high.