contagious rot in Cattleya new growth

[Orchid Whisperer]

Gypsum (or Plaster of Paris) is a great option, and inexpensive. Dissolve about a teaspoon (5 cc) per 4 liters water. It dissolves slowly, let it stand overnight. You can also add a similar amount of Epsom salts for magnesium. Both also provide sulfur, another nutrient.

Use a cup (250 ml) of this solution per 4 liters of water that you are going to apply to the plants.

You should still flush occasionally with pure water to avoid any build up.