How Can I nurse my ailing bamboo Palm back to health? and was the fungicide I used the culprit?

Hi ..I've had a potted bamboo palm doing beautifully for years, about 8 ft tall to the ceiling,...a couple of months ago I decided to spray the soil with a Fungicide (Garden Safe Brand) as a preventative, because another of my plants was infected. Since then the plant hasn't been doing well,,,seems almost sickly, stopped growing and lost half its foliage...I am wondering whether it is the spary that caused it...(although the container said absolutely safe and to use it as a preventative), and do you have any advice how I can nurse it back to health? thanks you

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