Answer: Grayish foliage usually indicates dead foliage. If you suspect it is caused by dog urine, adding lime won't help the shrub, nor will it deter the dog (they are creatures of habit). You can try temporarily fencing the targeted yew to keep the dogs at bay, and rinsing the plant off as soon as possible after the dog visits. Aside from re-educating the dog (and/or the owner), there's not much else to suggest.
Best wishes with your garden!
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