I live in the Denver area and just planted a Russian Sage that's
about 18" tall, bought from Home Depot.

I planted it in full sun ( about 5 hours a day of it? ) on a slope
with good drainage and just checked the soil with a water meter and
it's moist but not too wet.

The problem is, in the 5 days since planting, the leaves are
starting to yellow from the base upwards. What did I do wrong, or
what do I need to do to help this plant make it?