Synonyms for Marking down:

n.

reducing (noun)
diminishing, Discounting.

v.

cheapening (verb)
degrading, paring, lowering, reducing, trimming, depreciating, shaving, belittling, devaluing, deflating, debasing, Cheapening, Discounting, slashing, cutting, devaluating, diminishing.

Other synonyms:

n.
reducing.