re: 3-2-1 Ribs

There's nothing wrong with your cooking temperature at all. You can cook ribs anywhere from 225-350. There's more variables than just a generic timeline. There's some missing info here.....what type of ribs, how much did they weigh, fat content, type of smoker, was there any additional humidity present, how often did you open the lid/door, how long did you leave the lid/door open, and how long does it take for your smoker to recover your cooking temperature?
Don't worry, keep practicing, and most importantly....enjoy the process