arms not growing or getting stronger
iv been training now for around 5 years but only been serious for about 18 month , my full body has grew and got stronger in this time but my arms never seem to change , it might be because of my body fat % being too high but i was wondering if anyone had any advice , i have got the horseshoe shape tricep and alot of strength in my triceps but my biceps are ridiculously weak , i struggle to do 15kg EZ preacher curls with ful ROM ! , my bicep workout varies but is this is my usual regime:
3 sets of cable curls 8-12 reps untill failure
3 sets of DB hammer curls 8-12 reps until failure
4 sets of barbell curls 8-12 reps until failure
3 sets of DB curls on incline bench 8-12 reps until failure
4 sets of preacher curls 8-12 reps until failure
i always feel the pump through my workout and my arms ache for hours afterwards , i make sure i get enough protein and plenty of rest to allow the muscles to grow but they just stay completely the same , any advice would be great