Looks kind of like hard water residue to me, but it's hard to tell. Seems like it's more present on the older leaves, too, which seems logical with that train of thought.
A Google search for "hard water spots ficus leaves" yielded this thread which seems to align. The search function on the site itself can sometimes be tricky, but using Google to search for threads and info has been a sweet tool for me, FWIW.
White residue on leaves, trunk and soil is often calcium or other minerals.
caused by water evaporating, leaving dissolved minerals behind.
More common when leaves are misted rather than watering thoroughly.