Your over-training your biceps bro. Don't forget you train back as well. UR bi's get a lot of work with back. I would do barbell curls and pick two more exercises for 2 sets of 8. I believe you have way too much work in there. I have great arms and I don't train them hardly at all compared to the volume you have here!
Look like overtraining to me too. More complex movements like bench and deads, less volume on arms. My wrists are about the same size as yours it sounds like, my arms aren't huge but they are bad for a 6' guy.