Okay - gonna give my best guess and hit it with soap solution or neem after I prune it.

Seegaye,
Sorry noone answered your question.
I think you are right with your solution.
I use Organicide from HD on my shiny foilage plants.
It's totally natural and I can use it around my animals. Youo can even use it on edibles.
The next time your there, look for it.
You dilute it and it lasts a long time.
When your gardenia blooms, post a pic. I'd love to see it.

Thanks for the reply! They just finished blooming - was so nice! I had to douse that one with a product for pests in order to fix it. Oddly the other four plants are fine. They are quite close so environment is same / similar. I am not sure why only one was affected.

I will look for the Organicide next trip to HD! Apparently it is good to have something on hand when gardenias are around! Thanks again!