Nice aros! Pictures are in great focus two, beyond anything i could accomplish.
I don't think aros develop drop eye by looking at something. If you cross your eyes, for two long, they won't stay there.. I think something pushes it down. Whether it's fat buildup (though i doubt that) or some sort of liquid or whatever- i think something forces it. I don't think its a predator problem
since there's WAY more predators in the amazon then there ever would be in an aquarium. It could be carbonate hardness, ph, or whatever. Maybe calcium, who knows. The fact that neither of yours makes me think it's something in the water... But why?
Here's a wild theory (typical of me, lol): Aros get dropeye from high carbonate hardness. Let's say there's some sort of collection of liquid that is present behind an aros eye. If the water is hard, it causes this water to harden and pushes the eye downwards