I live in eastern Mass. Just planted gardenia bush a week ago. Now the leaves inside the bush are turning yellow.
Leaves Turning Yellow on a Newly Planted Gardenia Bush
Certified GKH Gardening Expert
It sounds like it went into shock, which generally results in yellowing of leaves and subsequent leaf loss. If your gardenia is suffering from shock, this article should help you: https://www.gardeningknowhow.com/plant-problems/environmental/learn-how-to-avoid-and-repair-transplant-shock-in-plants.htm