Non critical - on server load (7.0.4, probably been happening since 7.0.1) I receive a message stating:
20:37:17 [INFO] [PreciousStones] Adding flags column to pstone_players table
20:37:17 [SEVERE] Duplicate column name 'flags'
20:37:17 [INFO] [PreciousStones] Adding flags column to pstone_fields table
20:37:17 [SEVERE] Duplicate column name 'flags'
20:37:17 [INFO] [PreciousStones] Adding flags column to pstone_cuboids table
20:37:17 [SEVERE] Duplicate column name 'flags'

They happen each restart/reload.
Seems like these might be leftover debugging messages? Hopefully this can be fixed in the next build :)

fixed