Have you been watering it with hosepipe/watering can?
They are acid lovers, meaning they need soft water or rain water. Is your tap water soft? (as in no chalk)
As for the Miracle gro, it is not the best thing for it. If your ground is acidic then you shouldn't need to feed it much, if at all. If your ground is not acidic I doubt it would have survived this long! Your soil could be borderline (neutral) in which case the best thing you can add around the plant is pine needles. Until you find some add a cup of vinegar to a can of water each time you water.