Avoid using tap water if possible; instead use rainwater or distilled water. It will further cause brown dusting on the leaves as well as blooms. Brown, yellow or black or water soaked spots will appear on the leaves. If you notice brown spots on the tips and edges of leaves, this could be a sign of excess salts, chlorine or fluoride in the water. This disease is mostly seen on dracaena. If you prefer tap water, allow it to sit for at least 24 hours so that the chlorine and fluoride can evaporate. The disease will subsequently kill the leaf.