How do you cure? Are you working slowly to 61-65% RH and holding it there for 3 weeks? Do you use Boveda 62 packs to help? Keep the dry/cure process in the dark?
You could also try a UVB light. Get the small "ReptiSun UVB 10.0" CFL bulb for about $15 US. Put it on its own timer and turn it on during mid-late flower for 30 minutes per day at the end of the day. Increase the time while watching for any problems it may cause. (I just started using one and it seemed like leaving it on too long, maybe 3-4 hours, burned my fan leaves. But, I have a couple other "issues" going on. So, I don't know. Without someone else telling you a longer period is safe, I'd recommend starting at 30 minutes and working up.). Also, rotate the plant so different parts get exposure from day to day.
I've been growing Northern Storm Auto from marijuana-seeds.nl. I'm finding this to be a hardy strain, takes heavy feeding, bounces back from problems. I got 6+ ounces (dry) from my first 2 grows. My third had problems due to acidic soil -- but it fought the good fight with me and has bounced back in an amazing way. I'm looking at 3-4 ounces.
Anyway, that stuff is dank. After 3 weeks of curing at 61-65 RH, it's just frosty white. I have friends with high levels of tolerance who say "I'm done" after a couple hits. You could try growing one of these and see if your experience is strain dependent or peculiar to something about your growing/curing method.