We apologize for the delay in answering. We are not yet fully staffed with eXtension experts in the area of your question.
Kiwi, like well drained rich soil, a depth of about 2 to 3 feet. They do not like to be in standing water. They also do not like to be in areas where the cold air pools.
The optimum pH is 5.5 to 6. You may have to take a soil sample to find this out.
It needs full sun and plenty of water through out the summer. If it is a hot dry area, the vines may get too dry between waterings. If you wait until the plant shows signs of stress, it is too late. The fine root hairs have already been damaged, and the plant will spend its energy repairing the roots before it resumes growing again. Try to keep the water off the crown where the vine growth is. The crown is susceptible to rotting.
These are just a few ideas. I have included a link for you to read through. Maybe it is a few factors together that inhibit growth.