Your plant's leaves could be turning brown for a number of reasons and is probably stressed. Blueberries prefer well drained soil and a sunny location. While most plants prefer a more neutral pH, blueberries prefer a more acidic soil with a pH level of around 4-5. Because of this, it is good to fertilize them with an acid fertilizer (rhododendron or azalea fertilizers work as well as organic blood meal or cottonseed meal). It is important not to over fertilize as blueberries are very sensitive to too much fertilizer.