Zygopetalum spike randomly dead?
 

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A few days ago this was a happy pale green in color. Now suddenly black.

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Sorry about the small/bad images-- it's hard to see, but a few of the other new leaves have brown crispy ends, and most of the leaves are coming out looking like something has been nibbling at the edges? I have no idea what could be causing this.

I'm sorry that you have lost your bloom spike. I would remove all the black so that it doesn't spread. I'm not quite certain what causes this but I have noticed the leaves growing indoors look much better than the ones that grew outdoors and I suspect it is because I am watering from the bottom so water isn't getting on the leaves. I hope someone else can advise you.

:bump:

is the brown part soft and mushy ? is the pseudobulb affected at all ? best is to cut away the brown/dead and dousedab with hydrogen peroxide at least daily until the infection is gone. I have never seen that before and I grow a range of zygos indoors.

The brown part was soft, but now is dry and crunchy. The pseudobulbs all seem fine, smooth and green. The previous two spikes bloomed without incident, although the weird marks on the leaves were already there.

Well, the pseudobulbs are nice and green, but the leaves are dying. One pseudobulb appears to be pinching off a new pseudobulb... meanwhile a totally new growth spike is coming out from the base and new root growth continues.

I dunno what this plant is doing. Some kind of fungal infection at work maybe??

http://img.tapatalk.com/d/14/03/19/busepa9y.jpghttp://img.tapatalk.com/d/14/03/19/sava6uja.jpg

I don't really know why this is happening to yours. I only have two. One is a seedling, the other is a back-bulb division. On both, the older pseudobulbs have become leafless as the new growth has just matured. I have been watering from the bottom as these seem to be a little finicky about water getting in their leaves and I have been using a slow release fertilizer as the MSU fertilizer gave the leaves brown tips.
Hopefully someone else will be able to help you. Quite a few people seem to be growing these.