ACV question

There is one thing that has been bugging me a little... 

I've been no poo for about... 10 minths now and it's been working really well :)

basically I've switched to WO + ACV rinse and occasional diluted natural shampoo wash if my hair needs it and my hair looks really nice, feels nice, smells good when it's dry. I have hard water, trying to grow my slowly growing, fine, straight hair out.

but there is this one little thing that I was wondering about - I wonder if I am using too much ACV for my rinse.
I use about 1/4 and even more per cup (sometimes the ration is 1:1) which results in my hair getting prone to tangling and kind of... hard and 'crunchy' when it's wet. after my hair has dried, however, it's nice shiny and soft and doesn't tangle after I've carefully untangled my hair. 

a few days ago I used less ACV than I usually do and my hair was matte and tangled like crazy and in addition was dry but oily if that makes sense. terrible.

so what I'm really wondering is: how much do you guys use ACV per cup if you have hard water? And is that hard crunchy feeling normal? How do I know if i'm using too much - and what are the consequences of too much acidity?