Question
my indoor gardenia is thriving and blooming, but all the leaves are light green and lusterless.
please advise

Answer
Acidify the soil with aluminum sulfate, iron
sulfate, or wettable sulfur. Iron chelate may
be used on the soil or foliage. An
acidulating houseplant fertilizer can be
used to lower soil pH. Allow the soil to
remain evenly moist but not saturated.

Good luck!