Don't look like much. Like a scrape near the big rock. Maybe from squeezing in somewhere. Maybe coincidence with the EBA. I would say just watch for now. A little stress coat will help.
I was guessing more like another poly nipping them both at night. I've not kept poly so I'm not sure how likely they are to jump, but with cichlids I assume aggression to be the cause. Just saying there is a chance that these events are not unrelated.