Q.Gardenia
Recently repotted Gardenia .it is now getting yellow leaves is it transplant shock or something else it is being grown indoor in a high light location. its being grown in a fast draining organic compost potting soil

Gardenias actually prefer to be a bit root bound.
Make sure you have not chosen too large of a container.
Too much room in the pot, leads to overwatering and possible root rot.
Yellowing leaves can indicate a watering issue; too much or too little.
Soil should be moist, but never soggy.
Gardenias are a finicky plant and even more so in an indoor location.
They need a very high humidity.
These links will help you.
https://www.gardeningknowhow.com/edible/helping-a-gardenia-bush-with-yellow-leaves.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/growing-gardenias-indoors.htm