If it is bacterial leaf scorch, there don't appear to be any readily available remedies. Out of curiosity, what variety is this? How rapidly is the damage progressing? Where did you buy it? Do you have any other blueberries?

I've got one that looks like that. I think I forgot to water it a couple times.

My blueberries did that last year when it was very very hot and dry in spite of watering them frequently.

I do not think they are under watered, they get watered every morning. It is not very hot here either. I believe it might be a sharpblue, but not sure - have a misty nearby doing fine.

Short of water.
If you haven't yet mulched, do so.
To verify soil is moist enough, stick a trowel in it and look.

Its hard to tell from the picture but are those rocks around the base of the plant?