Perhaps the rabbit-eye blueberries grown in the south are deep rooted, but blueberries hardy for zone 6 or colder are certainly NOT deep rooted. A foot of good soil that drains well is sufficient.
Pine needle mulch is a wonderful thing, but contrary to you may hear, it does not produce acid soil. Blueberries are self-fertile; you don't need two kinds of blueberries to get fruit or to grow plants. But planting two kinds that bloom at the same time will yield more fruit than just one kind.
We can't tell from your explanation if pH is the problem. Pale or yellowing leaves that are not limp and do not fall off would be a symptom. If you determine that high pH is the culprit, you will need to redo the soil bed. Trying to amend or apply chemicals or fertilizer from the surface usually does not work because it is only a temporary fix. If it does, you will need to repeat applications at least twice yearly, and forever.
To redo the soil to insure proper acidity, mix a 1:1 ration of sphagnum peat and whatever soil you have. The exact ratio and the pH of the original soil is not important, as the resulting pH of any close combination will be adequate for blueberries. They thrive in a wide pH range of acidic soils. Thereafter, you might add some ammonium sulfate or ground sulfur (elemental sulfur) every 3 or 4 years. Do not use Aluminum sulfate.