Yellowing Vanda

[Irisha99]

Hi,
This beauty was just in bloom and seemed happy (see last picture). I cut off the spent spike and a week or so later one leaf showed some yellowing at its base. The leaf was in the middle of the plant. I cut off the yellow portion of it but looks like the leaves above that leaf are yellowing too. Seems like the stem has brownish look to it where the leaf started yellowing too. I am so sad about this plant because it’s been doing pretty well. Growing new leaves and had nice root system too.
I water it by dipping it into a basin full of water for 20 minutes or so. Fertilize once weekly by spraying roots with 20-10-20 fertilizer diluted gallon to 1 tsp fertilizer. What do I do with it now? How do I save it? Thanks!