Tony is correct about nutritional disorders or low humidity and temperatures.
But if you had mites, I can almost bet without seeing it that you still have it. Although the chemicals I listed may be difficult to get, perhaps if you have an orchid specialist in your plant group or some other plant group you belong to, may have it and or could sell you enough for a small fee.
But don't despair, you can always use other substitutes. It has been proven that very hot water sprayed on the plant, while not causing much harm can kill mites. I believe a temperature of 110 degrees F can be used effectively with almost no effects on plant harm. Having a mist bottle of cold water to spray on afterwards or working with a partner would definitely help prevent translucency from hot water. The hot water method isn't 100% but with frequent use, is very effective. I read somewhere on the internet that cinnamon used in a suspended spray solution is also very effective against mites and that is how we came about to have a miticide called CinnaMite (seriously) not sure where it is, but plug a few words into Google and see what you come up with. Also lemon juice used in a warm water spray solution also works, but you may want to experiment on a less rare plant first before use on your special plant.
While mites will concentrate in the growing tips, sometimes the removal of the tip and flushing it down the toilet or soaking in alcohol and discarding it would help remove the epicenter of the mite population.
Mites can be seen with a good pocket magnifying glass. They have eight legs as opposed to six on insects. Its also possible to swab them away with alcohol but care should be taken not to dry out or burn the growing tips.
Good luck and hope it recovers quickly.
One hint: Mites dislikes water, so frequent misting with water would help. Add a spreader sticker to the spray solution to increase viscosity. Mites don't like being wet!
