Don't ever automate the master volume fader, and don't ever touch it either.
The issue with your first track is that your bassline is overtaking the other instruments in the background. Your low and mid-lows are muddy, and they are overshadowing a lot of the mix.
Your second track's kick and bassline have a hard time distinguishing from themselves. Either increase the volume difference substantially, change the tone of the kick, or sidechain. I would also recommend more dynamic contrast with the sections--too much bass in the pre-chorus and chorus will make the chorus seem anti-climactic, for example.