If "lounges" means cushions
and they're already moldy, get them off the boat and clean them now before it gets much worse.
You prevent mold
by increasing airflow (add dorados or solar
vents), removing moisture (might need another small bilge pump
to get rid of small residue, or adding a goldenrod dehumidifier if you've got shore power) etc. Plenty of threads on that.
There are no miracle solutions, just the long standing ones, and if you can't get it warm, dry, with good airflow? You will have a mildew/mold problem. Which gets much harder to fix once it spreads.
If you make sure to stand up all cushions
before you leave the boat, that allows greater airflow around them, which also discourages moisture and mildew.