Are you getting leaks anywhere that might be causing the tank to sort of fuse together with eliquid, are you overfilling? How tight are you tightening the tanks to begin with?
I suppose it's possible that you have three ungodly hard to open tanks, (although I don't own them so I'm not certain) but before I run along and recommend tanks, maybe figuring out the problem with these might be helpful in the long run. Some tanks are easier to overtighten than others, and some are just easier to open period, but if something is happening to cause difficulty with all your tanks you might want to figure out what is going on, or try to at least.
And type of tank (MTL vs DL) or type of fill (topfill or not) airflow (top air or not) would probably be helpful if you want recommendations.
Anna