String quartet 160827

Here is my first in depth composition for string quartet (two violins, viola, and cello). I have some background in theory but only recently have been getting into actual composition. I'd love to hear feedback from some of you, as I want to get better and better at this. Thanks!

Your engraving makes no sense. Sorry, but I just don't get it.

1. m.1: C-flat and C natural shouldn't really be in the same measure so fast. Seems like you're in F mixolydian, so a B-natural would work just fine.
2. m. 2: Eighth note C in the bass tied to a dotted quarter C in the bass. Unnecessary, especially since you're in 4/4 and not 8/8.
3. m. 1-8: Is there a reason why the soprano has slurs, but your alto doesn't?
4. m. 17: What is going on in the alto voice? It's unnecessarily difficult, not slurred, and doesn't fit in the character of the piece, look for technical glitches.
5. m. 18: Beat 4... note? I recognize this could be a technical glitch, but again; hard and unnecessary. 
6. m. 29-33: Either the entire quartet is rubato or none of it is.
7. m. 30: No need for the ties, and the subdivision markings are weird. 3 hashes normally means tremolo, and especially here since 32nd's would pretty much sound like it.
8. m. 37: Are they now pizzing? You need to mark that.
9. m. 40: Having the triplet in rests is not necessary, and there are too many eighth note rests in the alto.
10. m. 45-48: More hard rhythms.

Look, I know that was a harsh review, but some of these are very conceptual things that should be hashed about before embarking on that kind of a piece. I mean it sounds fine enough (other than the hard alto passages), but needs work to sound and look a lot more coherent. 

Thanks for the feedback! I'm trying to learn as I have almost no experience with notation so your detailed comments are very helpful.