Blueberries like the same slow release plant food made to feed other acid loving plants. Miracle Grow makes a fertilizer for  azaleas, camellias and rhododendrons.  At one time Osmocote had a plant food for acid loving plants but that product was discontinued several years ago. You can also add peat moss to the soil and use pine needles as a mulch to acidify the soil. In some areas with alkaline soil the use of iron sulfate or iron chelate will help blueberries absorb iron so they won't suffer from yellow leaves. Keep growing, Marianne Binetti