Yellowing Leaves on Mountain Laurel / Cause ?

 I got one response to this, indicating it could be damage from voles.  Upon
inspection, I find no evidence of this.

Any other ideas please ??

Thanks !!

James

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Two years ago, I planted  3 mountan laurel bushes, about 8 feet apart.   All
three get the same watering, fertilizing, and sunlight.

The middle bush has leaves that are yellowing.  Perhaps a   1/4  of the
leaves are yellowing.   The other two look great !!

Any ideas why this is happening ?

Thanks for any help !

James