Thanks for your question. Other than dead leaves, the only symptoms of a problem are the red leaves, which appear to be sparser than the healthy plants' leaves. According to this article (http://www.extension.uidaho.edu/publishing/pdf/BUL/BUL0821.pdf)
"When drought stressed, the plants become stunted with red leaves and reduced berry production." I don't know whether you watered your plants during the drought months, or whether the plants (and their roots) are so close together that what water they received was unable to reach the roots. The plants appear to be very close together. The recommended distance is 3 feet apart in rows 8 to 10 feet apart. I can only see a bit of the soil, but am wondering if you have applied too much mulch around the plant, which can keep water from reaching the roots, as well.
Since these plants are well adapted to the Pacific Northwest, they are not plagued by many of the fungal and bacterial issues that other plants face. You would not want to plant another plant in this space were there evidence of some soilborne pathogen (bacteria, fungus or virus) that would infect the spot's new residence. I can see nothing in the photos that indicates that. I would recommend that you plant a new plant further away, just so it gets enough water. Similarly, you need to make certain that the remaining plant gets adequate water, and that it drains well.
Since huckleberry plants need acidic soil, I would invest $20 in a soil test and follow the lab's recommendations for adjusting the pH if it is too high. The closest soil testing lab to you is undoubtedly A & L Western Agricultural Laboratories whose contact information you can find here: http://www.al-labs-west.com/services.php?section=Soil%20Analysis
I hope this is helpful. Good luck!