Yellowing/Dente areas of lower Leaves, help!

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On my desktop it looks like a layer of sphagnum moss over bark, but I'm not sure. If the plant is in packed sphagnum moss, I would echo what Ray said. And if it hasn't been repotted in more than 2-3 years I would repot this spring when it warms up. If you bought your plants in flower at a market, they had probably been in those pots at least 2 years, and are due for repotting.

But, if you've been successfully growing it in sphagnum for months or years, you shouldn't change what is working.