Those particular types of LPS I have limited knowledge of and no hope of IDing... but even if they are the same genus, they could be a different species that don't like being up against each other. I made the mistake of putting Acan lordhowensis next to Acan echinata one time and my lord came off second best.
Check out where the recession is in relation to where the other coral has contact with it...
Check out where the recession is in relation to where the other coral has contact with it...
