Phalaenopsis with unusual leaf change: advice? Last resort!

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I also wonder if the plant is a bit dehydrated. the leaves don't look real plump but the picture may be deceiving. It looks like rock in the media so it may not be holding much moisture.

I agree, if it is the bottom leaf I wouldn't be too concerned. I myself would let it die on it's own and fall off unless it begins to look infected.