Could be one of several things, including drought stress, salty soils, or a soil pH problem. Most likely drought stress/heat stress. Young blueberry plants are especially vulnerable because their roots tend to be shallow and the top soil depths dry out most quickly. Also, young plants create little shade, so the soil becomes very hot. As soils dry out lack of water causes edges and tips of blueberry leaves to dry out and turn brown. This symptom is often confused with burn from a pesticide spray. They need to kept moist, but not waterlogged, meaning you need good drainage.
We don’t know how old this blueberry plant is? And we’d like to ask, is this the extent of the damage –just a few leaves?
For now, we recommend you remove the dead and damaged leaves. You might also want to consider a soil test, through the County Extension office, and tell them you are growing blueberries. Our soil is very alkaline, and they really love acid soil. You may need to amend your soil accordingly.