Such an interesting piece, and very effectively arranged for string quartet, I might add! The harmonic texture here was richly quartal — so much so, in fact, that I would consider doing away with key signatures in this piece. With so many accidentals already, having to remember which notes are sharped or flatted based on an arbitrary key doesn't help your performers.
I also noticed that you stuck mostly with p4/p4 chords. Nothing wrong with that as it provides a nice consonance while preserving that quartal 'edge' and, I believe, worked well here. You might, however, think about exploring the sounds of other quartal/quintal species, particularly those with aug4/dim5 intervals. That's one of the beauties of quartal harmony: the ability to expand or retract harmonic dissonance by tinkering with the interval of the 4th.
Which brings me to my next point of consideration. If you're going to use quartal harmonies, it might be useful to plan out your harmonic progressions. Quartals in any given key inherently do away with the triadic degrees of the key, and thus there won't be harmonic cadences. Musical phrasing must be achieved via other methods (which you pulled off quite well in this piece) and yet, by the same token, moving from one tonal center to the next becomes far more fluid. It's easy to get lost when using quartal harmonies; hence, a tonal 'map' tends to help out a great deal. (Not saying your piece suffered from this. Just wanted to provide a bit of advice in case you weren't aware.)
From a notation perspective, there were a couple of things to look at. First, slurs. Take a look at this one from the 1st violin at mm. 52-54:
The way this is notated, it would appear you really just want one big slur from that A to the final F. I assume you meant for the bowing to stop at the E and resume at the D, but that's not the way it's notated. There are also issues of competing ties and slurs, as in these bars:
It's conventional to extend the slur to the end of the tied note, provides a cleaner look. Someone correct me if I'm wrong... I seem to recall that that convention is dying away.
Lastly, there is the issue of unprovided dynamics between hairpin swells, as below (and above also, incidentally):
It's implied that the start of that C will be at the previously supplied dynamic, which is fine. The A-sharp will be played forte, which is also fine. But what about in between, where the closing and opening hairpins meet? Just a quick p or mp is all it takes, and it will mean the world to your performers.
Okay, I think that's enough for now. This is a marvelous piece and I'm glad you shared it with us! Keep up the good work!