First of all, I admit I haven't real knowledge about composition, still, I'll do what I can (with my poor knowledge both about music AND english) to help you :P
Bass are very important when it comes to provide a solid base to your song. I say that because I think
your song could improve very much just by adding a simple bass to hold it, otherwise, it soubds like... it lacks something. In my opinion, those parts where you decrease one octave, it sounds weird, it MAY be better if you just keep the voices in that octave (0:51 to 0:54). Also, I feel like the drums (or whatever D:) need a little more variation.
Finally, please don't take any thing of what I've said bad, as I'm saying it only to help you (try). I hope
you understood most of what I said o.O
Have a good day. :D