Sounds like an overwatering issue. Saturated soil decomposes anaerobically (no oxygen is available because the water takes up all the empty soil spaces.) This process stinks think of a swamp or sewer. Draceneas do need high humidity however. To achieve this, especially during winter months when heating systems tend to dry indoor air, create a moist atmosphere by standing plant pots on trays or saucers of moist pebbles. During its active growth period, keep the potting mixture moist but do not allow the pot to stand in water. During the rest period, water moderately enough to make the potting mixture barely moist and allow the top inch of soil to dry between waterings.