My four Greenspires were planed two years ago and have been doing beautifully. About six weeks ago I noticed that some of the leaves were browning (turning rather white, actually) and some of them were falling off. I did some research and found that they are prone to a certain fungus, but that the fungus is perceivable, and it's not evindent on mine.

Since then the browning has gotten worse, and covers about a quarter of each plant. I have no idea what is going on, or if there's anything I can do about it. The only thing I can think of is that they are planted in front of a southern patio fence, and get minimal sun during the winter. That said, they got through last winter just fine.

Any ideas? Thanks!