I occaisionally have similar issues. Sometimes I just can't get quite enough. The best thing I found that increased my pumping output was the MotherLove More Milk Plus Special Blend Tincture. It tastes gross, but it helps a lot. It's got goat's rue in it and that stuff is awesome. I had zero luck with the tea. There's just not enough of the good stuff in it. You'd have to guzzle it constantly all day! If you want to stick with the herbal tablets, you might want to add in Blessed Thistle, 3 tabs 3x/day. The fenugreek/blessed thistle combo is supposed to be really good. Honestly though, I've had the VERY best luck with that tincture.
A couple of general questions, though, are you sure your horns are the right size? If they're too small that can effectively pinch off the milk ducts preventing you from getting enough. An LC should be able to tell you for sure. Also, when was the last time you changed those white membranes? I change mine every 10 days. Are you pumping for AT LEAST 15 minutes at a time? You want to pump for 5 minutes after the milk stops flowing. Sometimes that means I have to pump for 20 minutes. I set a timer and whip out a good book so I can relax. Do you have a picture of your baby? I actually have some videos of her laughing and rolling around on my cell phone and that helps a lot too.
Good luck! You can do this!