Love the open sense of space.
Though, the piano sounds a little dry in the mix. It also sounds fairly midi-ish in that its volume doesn't change much. Piano is tough if you don't have a midi controller.
Second track I like that you open not on the tonic - that scores you some creativity points from me! :)
I think the strings still are a little midi-sounding - reverb can help this a lot. One trick with strings is to actually start the next note early so that the attack overlaps with the release of the previous note - this should help the constant muting/attack sound.
Last track:
Similar issues with the strings, but it is also a nice composition.
Well done!