Garden Pests and Diseases: Garden Phlox leaves yellow, little or no flower, 1 by swarring

swarring wrote:
I've got phlox in three areas of my garden. One area -- great, no problem, big fat happy blooms, and nice tall green stems and leaves. But the other areas, blugh. Leaves are yellow and disfigured, flowers are minimal. In another area, flowers are nil.

Problem areas: one is near (outside the dripline) a large Metasequioa. The other, about 30 feet away, is near (the dripline) a Norway Maple.

Happy spot: more out in the open, not near any trees.

I wonder if this is a pest, or maybe some effect the (two different) trees are having on the plant.

Can anyone help me out with this one?