Yeah I have a ton of discus..They become a little agessive with each other when trying to breed! One wild green I have eats small cardindals but I have never seen another one do it.(His buddy blue chews them to but he learned it from wild green)!
They are aggressive but they won't fight to dead.
What you may need to worry is they will stop the weak one to eat.
The result may be the weak one to be starved