What do you recommend when one muscle group grows slower than the rest of the body? Everything is growing but my arms.

Should I do more sets and/or exercises for this area or more forced reps and harder work or should I train the area more often or a combination of all three?

You may have to change exercises to find more workable movements.

Experiment with Tri-sets. That is performing 3 biceps exercises, one after the other. Then repeat the whole cycle again. Perform 4 cycles of three different biceps exercises and 4 cycles of three different triceps exercises.

Work to increase work load slightly each workout and gradually decrease rest time between exercises to zero.

Growth comes from a training frequency per muscle group of 2 or 3 times a week. No less no more.