Might we see an image of the whole plant, the pot it's in, and the top of the grow medium? Are the leaflets being shed all or primarily all older foliage? Have you changed the plant's location recently, or, can you think of any recent changes insofar as watering/ fertilizing? You are fertilizing? How long has the plant been in the same pot? Does the pot have a drain hole? Does your home make use of an ionic exchange water softening system (uses salt as the exchange medium).
The spots are probably not the result of a serious pathogen, perhaps not even a biotic pathogen. The shedding is most likely the result of one or more cultural conditions under which the plant is growing being at or beyond the limits the plant is genetically programmed to tolerate.
Al