Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
All I can say to this is that the discus must have been a fairly small one, perhaps ailing and somewhat weak, and the Cories must have sensed that - and the Cories must also have been starved for some food - that's the only explanation I can imagine.
In my experience with discus and cories, the cories stay well away from the discus, and the discus ignore them.
This is a completely new one on me.