Plugin Help PEX NOT WORKING

Everytime I reload pex I get this
Caused by: org.yaml.snakeyaml.scanner.ScannerException: while scanning an anchor
in 'string', line 578, column 16:
prefix: '&5[Sec.OfDefense]&f '
^
expected alphabetic or numeric character, but found [(91)
in 'string', line 578, column 18:
prefix: '&5[Sec.OfDefense]&f '
^
And the essentials format is using the {DISPLAYNAME} but instead of that groups prefix it actually uses the group name. HELP