How much pre-intro did you do? Sometimes it takes some time for them to establish roles. Mobutu it's could to be cautious.
Try offering two separate feeding stations, one high and on low, and best if not in view of the other. This can help where food aggression is concerned, and could help other issues as well. Offer the 2 feeding stations with the exact same food, then watch and listen carefully as they interact with each other.