So you are running six copies for the app server at the same time?
I'm a little rusty on this (its been years since I looked at JVM memory management in detail), but if I recall correctly, when a JVM starts up it asks the OS if it can reserve the amount of memory specified by -Xmx. If if can't it won't run. If it can, it then requests only -Xms memory for the heap. This can lead to a possible OOME later down the line if you don't have sufficient memory (RAM + swap) to hold -Xmx for all 6 app servers.