The good news is that Blueberries are relatively trouble free. The bad news is there are some fungi that attack Blueberries. See: http://oregonstate.edu/dept/NWREC/sites/default/files/pg_programs/berry/documents/107-113-blueberry_...

  Since the plants are on raised beds, it is unlikely but not impossible that the roots of the affected plant are too wet. If there is standing water near the affected plants, improving drainage will give roots a chance to heal.

 Since blueberries do not tolerate poor drainage raised beds should be 12-18 inches high and 3 feet across to provide adequate drainage. Since this year has been especially wet, it is possible the plant is in a location that is not draining adequately.

 When considering a plant problem, starting at the basics is always good. Blueberries require proper PH and are fairly heavy feeders, requiring the application of fertilizer to stay productive.

Blueberries prefer an acid soil with PH between 4.5 and 5.5. Having PH too high will result in yellow leaves with green veins on younger leaves.

 This article will help with the specific nutritional needs for mature plants: https://catalog.extension.oregonstate.edu/sites/catalog.extension.oregonstate.edu/files/project/pdf/...

 It is possible to visually tell if plants are getting sufficient nutrients. If plants are growing 10-12 inches a year, if leaves are green and yield is good the plants are getting sufficient nutrients. Covering nutrient and drainage issues are the first step in maintaining healthy plants. If plants are struggling and there is sufficient air movement created by proper pruning, proper drainage and proper nutrition, pests or diseases can be considered.

 The unusual wet winter unfortunately makes an ideal environment for bacterial blight and fungi.

Hopefully one of the resources listed will provide the answer to your struggling plant. Please follow up if you have additional questions.