Blueberries are wonderful garden plants.  Your plants seem to have marginal leaf stress caused by not enough or inconsistent watering.  Most of the water use by plants is through transpiration,  the loss of water which vaporizes from tiny pores, on  the underside of the leaves.  This summer has been so hot and dry that even normal watering has not been enough.  Blueberries have a very shallow, fibrous root system, so they're very susceptible to drought damage.  Usually one inch of water/week meets their needs very well, but this year, they need watering twice as often. 

This publication, Growing Blueberries in Your Home Garden, has good information on all aspects of growing blueberries.