Help with my 4 hens

Nothing. You are doing nothing wrong.

I'd take them off at 170-175, just because my kids would be eating them. Better safe than sorry.

Did you brine them? Butterfly them? Where are you take'n the temp of the birds? If a leg pulls off very easy, then they are done.

Don't worry, they are fine. If they are done early, fine. Don't sweat it.

First, welcome to SMF! Glad you found us. The only thing I can think of is the thermometer is up against a bone. Or maybe the chickens
dont like thier enviroment..........

Seriously, check th placement of your probe in the bird. Try the thick part of the breast or the thigh.

If they are already at 155F after 1 hour and 15 minutes, I would check to be sure your smoker is really at 220 and not some higher temperature and also insure as crewdawg52 suggested that the chicken thermometers were not against the bone. 165F is the new USDA safe cooked temperature for poultry but I also agree with BigAl on going a little higher just to be safe. It normally takes a longer period of time for me to smoke some drunken chicken and I have the feeling you are actually smoking them at a higher temperature that you think. Your chickens should be OK if they were cooked anywhere from 220F 375F as long as you take them out when once they reach at least 165F in the thickest part of the chickens internally.