From what I can see, it looks like the leaves got scorched along the edge, and the whole leaf, including the veins, turned brown. Did you see other symptoms, such as reddening of the leaves, splotches, or spots on the canes? Or dead or blighted blossoms? Did the plants produce flowers or fruit?
This looks more like an abiotic issue (such as sunburn, watering issue, herbicide/chemical drift, or soil nutrient problem), rather than a disease or insect. Blueberries need a consistently moist soil (but not soggy soil!). It is possible you are over or underwatering the plants. You can check the soil by digging down a1-2 inches to see if it is still moist under the surface. Be careful not to overwater, that can lead to root rot issues, and make sure the soil drains well. Established blueberry plants require from 1.5 to 3 inches of water per week, with each watering you want to wet the soil to a dept of 0.5-1 foot. The root system is relatively shallow and very fibrous, but devoid of root hairs (which increase the surface area of the root for water and nutrient uptake). This characteristic makes the blueberry plant very sensitive to changing soil/water conditions. This factsheet on drought stress in blueberries has some good photos of the symptoms for comparison purposes: https://www.canr.msu.edu/uploads/files/Blueberry%20Drought%20Symptoms.pdf
Have you or a neighbor used any herbicides or chemicals recently that may have drifted onto the plants? If not, you can eliminate that as a possible cause.
This could be a soil or nutrient issue. Marginal necrosis can be caused by potassium deficiency. Potassium (K) deficiency is relatively rare in Oregon. Leaves of potassium deficient plants may develop several symptoms, including scorching along the margin, cupping, curling, and necrotic spots. Low leaf K values may be caused by poor drainage, drought, or very acid soils. Typically, older leaves are more affected than newer or younger leaves. If you want to do a tissue sample, normal August leaf K levels are 0.41 to 0.70 percent.
It could be a soil pH issue, blueberries need a soil pH of 4.5-5.5. Typically, you would see yellowing of the leaves with green veins if the pH were too high, which I don’t see in the photos. But, if you haven’t tested your soil pH recently, you should do so (see: https://extension.oregonstate.edu/lane/events/soil-ph-testing-10).
Also worth considering is a soil borne pathogen, such as verticillium wilt (https://pnwhandbooks.org/plantdisease/host-disease/blueberry-vaccinium-corymbosum-verticillium-wilt).
Start by checking the water to eliminate over or underwatering as an issue. Consider adding some sawdust mulch to raise the organic matter and reduce evapotranspiration (allows the soil to hold more water). Test your soil pH to make sure it is within range (4.5-5.5). If you see other symptoms, or can eliminate water, nutrient or chemical drift as possible causes, then you can send some plant samples off to the OSU Plant Clinic in Corvallis for diagnosis: https://bpp.oregonstate.edu/plant-clinic. For more on Growing Blueberries in Your Home Garden, refer to: https://extension.oregonstate.edu/catalog/pub/ec-1304-growing-blueberries-your-home-garden

Thank you for your reply and I apologize for re-submitting the question. Please ignore the latest request.

If you didn't see any blossoms and had a dead cane, it is possible that you are dealing with a pathogen, perhaps a soil borne-pathogen such as verticillium (which would affect your vegetables too), or a virus. Laboratory testing would be needed to diagnose the problem (https://bpp.oregonstate.edu/plant-clinic). I still recommend that you closely monitor the watering and check your soil pH to be sure those aren't the source of the problem. You should also prune out and destroy any dead canes. 

Thank you for your reply. I will definitely look first into the soil ph and am making sure the plants are amply watered but no overwatered.

A&L Western has a laboratory in Portland, you can find their services and fees here: https://al-labs-west.com/. You can always ship the soil samples to the lab as well. There is a company up in Washington that does soil testing specifically for home gardeners, you find their information here: http://www.simplysoiltesting.com/. And check with your local soil and water conservation district, sometimes they offer soil testing. For a full list of laboratories that serve Oregon, refer to this OSU Extension publication: https://extension.oregonstate.edu/catalog/pub/em8677.