Here you can see the leaves turning reddish + falling off , most probably a deficiency or what would you say ?

Where is this plant located? Weather may play a role.

Another possible problem is that it's planted in dirt. Dirt is not the ideal planting mix for plants in containers.

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I've never heard of S. persica before, but looking it up, it seems to be a shrub/tree. I doubt the plant in the pot is a woody shrub or tree.

S. persica fruit are round and entirely different from the pictured seed capsules; they are not located singly on the stem. S. persica leaves are opposite rather than the compound leaves of the plant in the photo.

http://www.kew.org/science-conservation/plants-fungi/salvadora-persica-toothbrush-tree