Because your bass guitar is shitting all over your kick drum. Find the frequency where the kick is prominent at and notch that area out of the bass guitar. I'd say a Q of around 3 should be good. Secondly, you need to decide if the guitar or bass is going to take up lower frequencies. Because right now, they're clashing. I'd let the bass handle the lowend and hi-passing the guitars more aggressively. A multi-band compressor for the guitars would also be a good idea, too. Don't forget about the bass guitar either. Keeping that mofo in check is all about EQ and compression.