Every sound is in the same channel from what i can hear, try separating them into a different channel, and assign them to a separate mixer track as well. This will stop allot of the sounds fighting for control over the same chan. If you hear a sound all the sudden get way softer than you intended it when another one is starting to play, this very well may be the answer. You can hear what im talking about in the first 10 seconds.
Try Using any type of param EQ and clean up allot of these sounds. They are all sounding on the muddy side. The kick was way too low,i say this allot, but the kick should be around -6 or -8 db pre master. The kick should also be the loudest part of the mix, followed by the bass as a close second. The bass wasn't really following the lead key changes all too well, that's a simple fix however. Nexus is a powerful tool when used right, i would suggest looking up some tutorials over how it works.
+ 12 db = 400% volume increase.
+ 6db = 200%
+ 1 dB = around 10%
0 dB - No change.
- 6 dB = 50% volume decrease (half the original level).
- 12 dB = 75% volume decrease (to 25% of the original level). ( image line db guide)
Hope that helps in some way
Zafrece