In order to cut down or eliminate spotting you need to stop misting on cold dark days, only mist (if you must mist) on bright sunny mornings. Spots occur on leaves that have water droplets sitting on leaves for long periods. You must also increase the air movement. I have a fan blowing directly towards my zygos so the leaves are always blowing gently in the wind. They don't like cold stagnant humid air.
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