Q.Gardinia
My gardenia is so beautiful, usually this time of year? It’s outside. Mostly shaded. While this year had a beautiful profusion of blooms, within 2 days of each bloom they turned yellowish and with another 2 Days yellow blooms fell off. No fingus or aphids that I can see. Any ideas as to what caused this? Leaves are thick and green.

This article may help you diagnose your gardenia bloom problem
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/no-flowers-on-gardenia.htm