I have read one study (provided at a seminar two years ago) that shows that the additional roof vents can reduce ventilation of the total attic space.
Air moving over the ridge vent draws air from the attic. The added vents a few feet away from the ridge can be providing the replacement air instead of or more than the soffit vent, as originally intended. Or, the air that the added vents are actually drawing is coming in through the ridge. In any event, under these conditions there is insufficient ventilation in the total attic space.
Look, for signs of moisture/damage in the bottom third area.