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Corrosion might 'eat' a very small component like an SMD component (surface-mount type), but if so, you would see *some* sign of their presence or former presence. For instance, a trifle of eating-through of the holes in the circuit boards in which they were mounted, might show up, if the leads got eaten away as well as the components themselves.
Or you should see the remains of the leads sticking out of the circuit board. Or at least, see the remains of the leads of the missing components sticking through to the other side of the board. Such evidences would be indicative of the former presence of a mounted component soldered into place.
But there might well be blank/unused space on a circuit board. Some revisions of the same board do not have some components; or some revisions of the board might have had the presence of those components edited out 'at the last minute' as it were, after the boards and their layout had already been completed.
(A photo or picture, of both sides of the board in that area, might indicate something more to me about the question.)