I'm new to axolotls, so I won't claim to know the right answer to your question, but I do remember reading that they're less aggressive as adults, so whatever "disputes" their having now, they will be fine once they pass through puberty, so to speak. I hope that helps some. (I would think that, if you keep a watch on them, and they don't continue fighting, they'd be fine, but separate them if you catch them at it again. Do they have enough hides to retreat to, and get some distance from each other?)