Plants in the heath family form a relationship with a specific minor class of fungi: ".....ericoid mycorrhizae, so named because they are restricted to the Ericaceae, the heath family, and some closely related families. The Ericaceae are familiar to [us] in the form of blueberries, cranberries, sheep laurel, rhododendron, etc....."
Given you live in west Oregon; I'd suggest going out and getting some soil beneath a healthy wild huckleberry and inoculate your blueberries and other heath plants.
Speaking of huckleberry; they grow extreeeeeeamely slooooooow!
Also; probably should have some sand in your mix
