I had the same problem for quite some time. Now through proper training, they finally started growing and look good. You need to make sure your making a mind-muscle connection with your biceps. That is the most important thing. Make sure you are isolating and thinking about them for every rep. Lose the exercises your doing now and use more isolated movements, and don't worry about how much your lifting. Work your tris and biceps , together, twice a week. I do monday and friday.
Do alternate dumbell curls, and make sure you go all the way down, all the way up w/o using your shoulders, perfect form. When you get to the top, turn your wrists to you can feel the bicep pump. do it everytime. think about every rep.
Do reverse grip straight barbell curls, all the way down , all the way up.
Concentration curls, do perfect form , all the way down up, Do 4 total sets, the last one till failure. If your using a 30 say to begin, grab a 15lb to finish them. You should feel a good pump.
Bent straight bar
End with straight bar cable pull, work arms individually or together, whatever feeld better.
This made mine grow. I was discouraged and thought I couldn't do it. Just concentrate on what your doing. If you want it, work hard for it. Remember the mind muscle connection-