I'm wondering if they "never fight" and now have "pronounced" scalpels because they are defending themselves from each other by display? My plecos swim with their "chew chew" (armored cheek bristles) in full display as a warning to all the other plecos in the tank, "Don't mess with me or you'll get this." Even though they should all fight constantly they never do. They all have their place both in territory and dominance in the tank, yet they still do these little displays that they wouldn't do if they were in the tank by themselves.