Spiders don't affect plants but they may have just been a brood of spiders that had recently hatched out. Perhaps they were there to eat some other insects on the plants.
Dropping leaves is usually a symptom of a root problem. In a container it is easy to keep the soil too dry or too wet for a time and this will be followed by a leaf drop. Check the soil and keep it moist. Move the plant back out to an area with bright light but not suddenly into a direct sun. The plant needs light and won't do well indoors for very long. Hopefull it will recover and resume new growth. In winter it will need to come in to a bright spot as it can't take the freezing cold.
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