In my pursuit for massive arms, I've been working my triceps exceptionally hard. I have recently noticed though that the outer head is growing nicely and I'm getting the horseshoe look that is so nice, but the inner head of the tricep seems to be lagging some. From looking at medical anatomy diagrams, this inner head seems to be the larger of the two heads of the tricep. It is still growing, but it seems that the outer head is leading the growth. Is this growth form of growth normal and I just need to keep going? Or do I need to add in different tricep exercises that focus more on the inner head? What are some exercises that focus more on the inner head than the outer?
Right now, tricep exercises revolve around the following:
2-arm overhead dumbbell press
triangle bar pushdown / rope pushdown / reverse grip pulldown (one of these as I do what I feel like that day)
Thanks for the help