Answer: Dieback is often a mechanism to offset root loss. In my experience, the first thought here would be transplant shock and root damage causing underwatering, although overwatering (lots of rain and a heavy soil) could also be a possibility. A slope should be sufficiently well drained but it could also contribute to moisture stress if a plant is suffering a root problem, while spot watering combined with rain could contribute to a root rot or overwatering problem. Additional fertilizing is not usually a good thing to do when a plant is ailing because it adds the stress of extra growth. Leyland Cypress does not strictly require an acid soil and in fact is very tolerant of a wide variety of soils and fertility levels. It is, on the other hand, subject to numerous problems, and the transplant process could have exacerbated an underlying problem you were not aware of before. Because of that I would suggest you consult with your county extension as to possible causes for the browning and see what they suggest. In the meantime, keep the soil moist but not soggy and mulch to prevent competition from weeds.
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