This feels like you have many units that drink much, so your rum production is much lower than that of the other two. Am I right?

You have about 35k troops.  Each troop consumes a dedicated amount of rum.  You can reach negative rum production if you get enough troops in relation to your total rum production.

Your options are upgrading productions, reducing consumption, joining a group with an upgraded bastion, and pardoning some of the heavy drinkers at a Presidio.  You can also raid other havens, complete prizes in hopes of a rum payout, or purchase it from the smuggler's den.  The final method would be to kill off a bunch of troops to eliminate their hourly consumption.