If you have a lot of pine/spruce trees then it's possible that your soil is too acidic, as you mentioned. Have you added lime to the soil to raise the pH? I've added some lime to the soil in my front yard because I have a huge blue spruce tree in the front and it's slowly killing the grass under it. The two hops I have planted there have done well so far.
You can also try digging cattle or horse manure into your soil. One last thing, I read somewhere that if the soil is lacking calcium that that can interfere with nutrient absorption by the hop. I actually watered my hops with watered down expired milk. One of them wasn't doing that well - very pale green leaves on the new growth and pale veiny patterns on the older leaves. Within a week of using the milk the plant had very deep green leaves everywhere.
