Does anyone know why some of my gardenia flowers are blooming yellow and others white but all on the same bush? What kind of fertilizer should I use and how often? The bushes have been in the ground for about a month and are blooming like crazy I'm just worried about the yellowing.

I think you can correct the yellowing with one simple method. Gardenias are like azaleas and camilias, they like acidic soil. Increase the acidity in your soil by adding used coffee grounds. Sometimes the simples and most inexpensive solutions are the best. That's why english gardens always flourished... simple solutions.