Gardinia

Question

planted a few month ago its white flowering but some leaves are turning a yellow to light brown

Answer 1

This sounds a lot like root rot. Fungicides and cutting back on watering, if possible, can help. Here are some articles that will help you:

https://www.gardeningknowhow.com/ornamental/flowers/gardenia/common-gardenia-diseases.htm

https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

https://www.gardeningknowhow.com/ornamental/flowers/gardenia