2002 F350 battery help?

Yesterday I drove it to work.. no problem.. lunch was at 7:30PM .. still no problems. I left at 10 PM and the batteries were completely dead. I jumped the truck and it made it home with no problems. I then used a battery tester and both batteries read 13.2 (normal) This morning the penger battery was completely dead, but the drivers had only fell to 12.4. I had the battery tested and it was good. I also had the alternator tested and it was good. Both batteries and the alternator are less than a year old. Any Suggestions?