I would check the ph of the soil first. Blueberrys need between 4.0 and 5.5. From reading about them, Blueberrys also require well drained soil and lots of direct sunlight. Plus they like airflow between the bushes. The lack of any of these can stunt a Blueberry plant.
Pa has a huge problem with acid rain from the coal buring power plant smokestacks in other states. It isn't just the Blueberrys that are suffering, it's the whole forest ecosystem. If the ph dipped below 4.0, it could cause a problem. If for some reason the ph is above 6, Blueberrys leaves will turn yellow and eventually die.
More than likely, trees are shading the plants or the soil may have changed enough that blueberrys, wild or otherwise, wont grow. You can contact your County Extension Agent. I am positive he will have an answer.