Question: Black leaf bottom

[dend321]

I have a Rlc. Prada green deluxe that I have been successfully growing for some time. A few months ago it put out a new leaf and was doing great, but suddenly, about a week ago the base of the leaf started turning reddish and then started turning a shade of black. The pseudobulb turned limp, black, and thin too. What might be causing this? It wasn't put in a new location, but I started turning the lights on in the room but maybe that only added 100 footcandles, not much. And the room is dim to begin with. I water about once a week letting the medium dry out and I hadn't fertilized in about 1.5 months but use msu fertilizer when I do. And all the other leaves look fine too. See photos attached.

[Ray]

That growth is dead. I'd remove it and use a q-tip to dab the wound with cinnamon.

Just a guess, but it looks like water may have gotten down inside the sheath.

[estación seca]

The way that growth died is classic for underwatering of Cattleya seedlings. Once a week watering for a small seedling in that large bark is probably not enough. The pot is far larger than I would have used.