From the appearance of the dry, cracked soil, I'd be wondering about lack of/insufficient water to the rootball. Looks like your plants need a good layer of mulch to help maintain soil moisture levels.

Also it would be best to clear out all that competing vegetation. If the pH is right for blueberry it's not right for many other plants. Separate your crops if possible. This will help maintain consistent moisture and fertility for the blueberry.

As lucky_p and fruitnut have suggested, this certainly looks like a moisture problem. I let a couple of my potted blueberry bushes get too dry last summer, and their response was very similar to what you're seeing -- rapid leaf desiccation. The good news is that the plants survived and have cropped well this year, so, if you haven't already, water them immediately and pay close attention to moisture levels going forward.

The palnt got a gallon water a day, isn't it enough water?? Plus the soil is clay, will it retaining water much better?? My other blueberry plants next to it did not have leave the same problem. Why only this one??

blueberries won't get fireblight. They can get a disease called stem blight. You can prune it out. However, your cane is still green so I doubt this is the case. Your soil looks dry. Keep soil PH bewtween 4.5-5.2

Blueberries have a root system that is not very efficient at taking up moisture and nutrients. As mentioned above, any plants near by will be better at stealing what is available before the blueberry can absorb it. I think you need to make a choice between blueberries or those other plants. My guess is that the PH isn't low enough either. Did you work a lot of organic material into the clay, and adjust the PH, before you planted? Do the plants that are doing OK have a more organic soil, better PH, more sunlight, or less competition from other plants?

Soils with a large percentage of clay are interesting in that, while they can hold more water than other soil types, the super-small clay soil particles also hold water more tightly than larger soil particles. What that means is that, due to the power of adhesion, the moisture level below which plants will be unable to extract water from the soil will be higher than in other, coarser soils. Moreover, the cracks that form in clay soils as they dry and contract accelerate moisture loss from the top layers of the soil. Finally, because clay is very susceptible to compaction, it can be difficult for roots to penetrate, which may limit root growth. This combination of factors can make gardening in clay quite difficult (I know from experience). Given the fact that blueberries have inefficient root systems to begin with, blueberries and clay don't mix all that well. As other have suggested, for whatever reason this particular bush is probably being out-competed for the available water. It might have a smaller root system than the adjacent bush, it be closer to other plants that are more efficient at water uptake, etc.

Thanks all . If it just a water issue, not any disease issue that is a good news. There are 10 plants in a row, the rest doing very well, have big berries. This one was newly planted from 2gl pot where it grew so fast, it outgrow the pot and get top heavy,often blow down by the wind so I decided to plant it in the groud. The soil had a lot of peat moss and some sulfer mixed into it when initially I prepareed the area. However, it could use more sulfer to keep up the ph level.