Are they Electrohome GO7 monitors? If so (maybe even if not), there may be 6 posts on the PCB on the left back side (3 labeled horizontal, 3 labeled vertical), 2 of which are wired with bullet connectors. 3 of these connectors are for the vertical positioning, try connecting the bullet plug to the middle post (or if already in the middle then the post labeled 'down').
Do this with power off, obviously

.. if it isn't a GO7 or doesn't have the posts, I wouldn't have any other suggestions
