planted this Spring - plums thriving, apples pitiful

I planted 2 apples and 2 plums at about the same time this Spring. They are all within 50 feet of each other. The plums are thriving and the apple trees really look pitiful. I fertilized them the same and tilled the soil in an 8' circle for all 4, mixing in some mulch and sand. The only difference is that I think I had a little bit more mulch when I planted the plums. Since the conditions and sunlight and soil are the same, what could account for the difference?
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Lyne wrote:

Are the apple trees appropriate for your area?
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Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8b
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Describe pitiful. Mine had the leaves turn brown and looked real sick. Then I had two cedar trees removed that were pretty close, and never had the problem again.
Dwayne

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