I had the same thing happen to my Zygolum Louisendorf, bought it in full bloom, but when the new growth unfurled it's leaves, they seemed sticky and then slowly turned that same color. It bloomed anyway, but the leaves dried up and died. Same thing happened to the following growth. It only kept the leaf on the oldest bulb.
A grower in the Toronto area told me he had the same thing happen to a batch of Zygonisia Blue Birds and to other plants of his in the Zygo family. He told me the change the media and soak the whole plant in a Physan 20 solution. It's what worked for him, even if he never knew exactly what the cause was and no other plants ever had the same issue. I did it for my zygo and it pushed a new growth and the leaves seem normal this time!
I also water it by soaking the plants in a bucket for a while. I think getting water on the new growth by accident might be what caused that for me. And, because I am a very bad person and I soak several plants in the same bucket, I think whatever fungus this is might be targeting Zygos only if that's at all possible? None of my other plants caught this and I had to have shared that water with phals and catts before I noticed the problem.
My solution, Physan spa treatment
Whichever fungi is the bane of our zygo leaves doesn't like it at all.