Hi hfams300;
Welcome to the forum.
Several things can effect how your smoker performs. You didn't mention if you got your temperature reading from the gauge on the door, or if you have a third party remote thermometer. The door thermometer is not accurate once you have food inside the cabinet, and it could read lower than the actual temperature. If you have a remote thermometer, for the best accuracy, place it on the bottom rack, and at least a couple of inches away from the meat. Setting the meat out for 1 to 2 hours, prior to placing the meat in the smoker does help.
Another factor could be moisture buildup. Two six pound chickens are a huge load. Chicken with skin will release a lot of moisture quickly, and if too much moisture builds up it will bring the temperature down. Keep your vent 3/4 to fully open when smoking/cooking chickens with skin, to allow that moisture to escape.
Ambient temperature and wind are notorious in bringing the cabinet temperature down - especially the wind. Some things members do to help with heat recovery is to place a preheated brick near the water bowl. Many pour hot water in the water bowl, at the beginning of the cook and when they refill the bowl. If it is a windy day, do your best to block the top and side vents from the blowing wind. Many members, as a more permanent solution, have built or bought a cabinet that will protect the smoker from the wind.
