Cattleya black new Leaf tips

[tucker85]

I agree with Leafmite and Silken, any time new cattleya growth gets fungus problems, it's a sign that the plant is not getting enough calcium. The crushed oyster shell, that you mentioned, is one possibility. Some growers use dolomite lime to increase calcium. Another option is to switch to a cal/mag fertilizer. Personally I use a supplement called MagiCal that you can buy in hydroponics stores.