Chlorosis is evidence that the yew isn't getting or processing the nutrients it needs to produce healthy green foliage.  

In many cases this happens because, although the nutrients are present, they are unavailable in high pH soils. 

However, in your case the soil pH (6.8) is optimal because yews are adapted to soil pH 5.3 to 7.8.

Because soil pH doesn't seem to be a factor, the challenge is to determine what's causing the chlorosis.

The following publications discuss this problem and what to do about it.

https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/insects-pests-and-problems/environmental/iron-chlorosis

https://extension.illinois.edu/plant-problems/chlorosis

http://apps.msuextension.org/montguide/guide.html?sku=MT202205AG

Thank you so much for your response.

University of Minnesota Extension doesn't provide the service or assistance you need.  However, certified arborists have the training and experience needed to do that.  If you decide to hire one, ask about his/her expertise as it pertains to shrubs and chlorosis.

This publication explains how to go about finding and hiring a certified arborist:

https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional