I have been trying to figure out what might be causing the die back and slight yellowing of several of my Juniper bonsai. Water rates are okay, fertilization is sufficient, so now looking into pests. I found a recipe for spider mites that I will try for the next couple of weeks. The recipe is here: http://www.mellobonsai.com/care/Miticide.aspx
Started this application on 7-15-2012.