Question
The developing flower buds fall off the gardenia plant before flowering.

Answer
Ruben:

These symptoms do not sound like a bona-fide contagious disease.  One possibility is the presence of tiny flying insects called thrips.  Examine the unopened bud carefully. Pull it apart and look inside closely at the area where the petals attach at the base.  Thrips are very fast runners and small- much like the size of a 1/2 gnat, so look quickly.

Gardenias can be temperamental.  Another possibility is the climate.  Common causes include low humidity, over-watering, under-watering, rapid temperature fluctuations, cold drafts or change in plant locations.  If it has been hot where you live, this is probably- my best guess if you do not see any thrips after you examine a few buds.

Steve