This is a really lovely piece! I feel the mix is pretty good, especially considering you did it while composing. The instrumentation and development of the piece are super interesting too! Most of the sound design is lovely :D
The melodies and chords, to the most part, are really, really nice!
There are a couple of rhythmic aspects to the melodies at times I feel could be improved on, like the piano interlude at 1:55. Like, the interestic rhythmic choice at 2:03 didn't really work for me in this particular instance, with the piano (I heard it working well for some of the other instruments though).
Nice ending too.
P.S. You almost used my favorite melodic line at 3:14 :'p