I have the same problem. What I've notice is that if I focus to much on my biceps/triceps, they don't grow that much. These musclegroups are very small compared to the rest of the body. To train them to often isn't very smart because they are involved in lots of other musclegroups. If you want them to start growing. Do heavy, but very controlled lifts like Weighted Dips for start with lots of warmup, do 3 work set heavy. After that Scull chruncher 2 sets, heavy but never to heavy, to know what is to heavy try to work with just the triceps and not the shoulders/chest when doing these movements. Dips are supposed to be narrow grip going down just about 90 degrees with your arms. Not to deep that is. Third excersice you can try kickbacks, 2 sets. After this I go over to biceps and do heavy lifts biceps curls shoulder wide grip with a barbell. I do 2 warmup sets and then 3 workset. After that I do hammercurls, and I must say I really love these, 2 sets, after that I do what ever feels right that day, what ever that would be..
Last 4 weeks I have focused on my arms and tried to do short, very intensive reps/set 2 weeks heavy(3-6 reps) 2 weeks 6-12 reps, and it seems my arms are starting to grow.
I train my arms on wednsday mornings and then I bump my calorie intake with 1000cals, the day after is always off and also 1000+ cals.