Here is what I think: I think that your exercise selection is good, but I think that you are using a few too many sets for such small muscle groups. I suggest that you also alternate exercises each workout. Here are some possibilities below:
Triceps
Workout 1 -
1. Close Grip Bench Presses - 3 x 8-18
2. Cable Press-Downs - 2 x 8-10
Workout 2 -
1. Parallel Dips - 3 x 8-10
2. Two Hand Overhead Dumbbell Extensions (Heavy) 2 x 8-10
Workout 3 -
1. Skull Crushers (lying tricep extensions) - 3 x 8-10
2. Single Arm Dumbbell Extensions - 2 x 8-10
Biceps
Workout 1 -
1. Barbell Curls - 3 x 8-10
2. Incline DB Curls - 2 x 8-10
Workout 2 -
1. EZ Bar Preacher Curls - 3 x 8-10
2. Hammer Curls - 2 x 8-10
Workout 3 -
1. Seated Alternate DB Curls - 3 x 8-10
2. Reverse EZ Bar Curls - 2 x 8-10
Forearms
Workout 1 -
1. Behind the Back Wrist Curls - 3 x 12-15
2. Reverse Dumbbell Wrist Curls - 2 x 12-15
Workout 2 -
1. Cross Bench Barbell Wrist Curls - 3 x 12-15
2. Reverse Barbell Wrist Curls - 2 x 12-15
Workout 3 -
Dumbell Wrist Curls - 3 x 12-15
Rollups (A Stick, A string, and a Plate) - roll up a couple of times.
Remember, the arms are small and are used when training back, chest, and delts. . .be careful.
I personally stick to one basic exercise for each workout, then I rotate. . .I have no intention of forcing my methods on to you. All I think you need to do is lower the volume.
In between your sets. . constantly stretch the arms. You might want to consider giving arms a seperate day. Here might be an option:
Day 1 - Arms
Day 2 - Legs and Abs
Day 3 - OFF
Day 4 - Chest and Back
Day 5 - OFF
Day 6 - Delts
Day 7 - OFF
or a 3 day a week routine:
Day 1 - OFF
Day 2 - Arms
Day 3 - OFF
Day 4 - Legs and Abs
Day 5 - OFF
Day 6 - Chest, Back, and Delts (2-3 exercises for each mus. tops)
Day 7 - OFF
I hope some of this information helps
Good luck!