I liked all of these tracks, there is a big difference in mood between them, especially 2 but I definitely feel like it follows on from the first track quite nicely, feels like the boss theme for the previous tracks area theme and I could hear all the tracks on the same soundtrack without feeling like any are out of place.
The first track especially I can hear the Yume Nikki influence in the first section which sounds great but then the drums, melody and bass you add in really take it to its own place too and sounds just as great, develops nicely as well.
I think the mixing is pretty good but could use some improvement in places, i.e. not sure about the kick and snare being panned hard left and right in the 2nd & 3rd track and I think to really sell the underwater theme you might want to use a heavier amount of delay and reverb to really create that wet underwater spacious feel. But It's still definitely acceptable and doesn't hurt the listening experience.