Check for spidermites (which love thin-leaved plants). As leaves age on such plants (that are eventually deciduous), mine tend to look like that without bugs... they just get ugly leaves, so it could just be that, unless you can actually find something on the undersides of the leaves causing issues, likely nothing to treat.
Thin leaves, spidermites are always suspect... a good spraying with something that has a miticide in it would be a consideration. Or just some neem oil (with a bit of soap) will knock things down for a bit - if you can't identify a pest so that a suitable treatment can be used.
I would agree, advanced spider mite attack. Whenever you see the slightest thing wrong with leaves on thin-leaved orchids, look carefully for spider mites.
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Remember, mites are arachnids, not insects. If you have a pesticide such as Bayer's Advanced 3-in-1, it does include a miticide as well as insecticide, though in small amount. A miticide is what is needed... insecticides aren't particularly lethal to mites.