Established plants can get to 8' just from stored energy. The one thing about new plants is they'll put more energy into deep root development so upwards growth will likely be slower. So, energy probably will be used sooner (1'-3'). Hopefully you prepared the soil before planting to help with some of the nutrients.
I shouldn't have said that fertilizer isn't warranted. I was making an assumption on the amount and type used (e.g. Miracle-Gro). I also was thinking too much about my own growing location. I'll be doing a side dress of compost this week with some bone meal and maybe some blood meal. Something like Miracle-Gro won't be used until faster growth where most of it can be used.
Great Lakes Hops has good info on growing here:
http://www.greatlakeshops.com/hops-blog/grower-notes-spring-2016
It seems maybe a granular fertilizer would be a good choice to boost your plants.