Black rot on leaves?
 

These orchids really keep us on our toes, don't they? :tombstone:

I have this C. lueddemanniana since last year and it grew a wonderful pseudobulb and now is working on growing a new one (which is fine, for now). In the past days I observed some purple markings on the back of the leaves, that now are spreading to the front as well. No soft spots, the leaves look normal except for these spots. It is growing in Vanda light, the kind that makes them almost bleach.
What is your opinion, should I take the scissors out of the drawer?

Thank you

I am not sure what is causing the purple variation. As long as it is purple and not brown, it is not likely to be a bacterial or fungal infection.

Maybe you can find some answers on this website:

http://staugorchidsociety.org/PDF/Or...ySueBottom.pdf

Thanks for the link, what a great resource to have on hand.

The areas are purplish-brown, but not sunken or watery.
I cannot believe that it's going this way, it was one of the nicer seedlings and I was really looking forward to its blooms.

You sure they're not burns? It is very odd for a disease to emanate from a broad, central part of a leaf.

I do like this link quite a bit. I am sorry my monitor doesn't show me the colors more clearly so I can take a better guess at what is happening to your Cattleya. Reddish-purple is usually okay: usually means higher light but could also mean a nutritional deficiency. Brownish-purple is more concerning.

I would sugest to move it to a location with lower light levels just to see if the spots disapear.

Read this.

I am no expert but just reading through the pdf shared above (thanks leafmite!) it seems possible it might be magnesium deficiency? The photos don't look quite the same, but purple discoloration in the middle of the leaf sounds right. So maybe try watering with epsom salts?

It looks like a thermal burn to me, too. If these were young leaves it also might be insufficient water.

Thank you all!
It might be a ledburn, as the whole fixture colapsed on them and burned some spots on the Vanda leaves while it touched them for around 20 minutes, and probably this was around. But that still doesn't explain the huge dark patches that don't even correspond on both sides.

I will isolate it and wait for the new growth to mature, that is if it gets there, and then evaluate the plant's condition. Such a shame :(