Yellowing junipers can be a sign of too much water or poor drainage - poke your finger in the soil to see if it is wet. Not enough water can also show up as yellow needles at the tips. A third reason could be lack of nitrogen and iron in the soil - is your soil very sandy and infertile? Perhaps you can send a photo and I could make a better guess at what is going on with your yellow junipers. Keep growing, Marianne Binetti