I find with Dracs that they are extremely sensitive to salts in the medium. RO or distilled or rain water is a must. Also if they get too hot the leaves will turn like that. As has been said low light (less than 1000FCs) lots of water (they like to stay damp to wet), coolish temps (under 75-80 - at least at night) will help. A mix with at least some sphagnum (like you would use for Paphs) is necessary as they really shouldn't dry out.