You got any multiband compression going on? Any ways I recently started watching ahjteam's videos and this may help you I know it helped me understand how to tame those frequency's. As he says you listen with your ears not your eyes. Find the sweet spot for each instrument. Oh and I forgot to ask are you panning your instruments? Bass heavy instruments stay in the Center while other pieces of the drum kit/synths/guitars can be panned. I think the video also explains this.
http://youtu.be/TttC7LyrMnQ -Mixing Low End
http://youtu.be/N1uGia-LXL4 - Moving things in the stereo field.