I have a two year old gardenia that by all accounts is healthy. It is growing well this season and continues to flower. However, I have had a problem with yellow leaves. It is an eye sore!!! I read that leaves on old growth will turn yellow as the plant moves magnesium to new growth. However, it is new growth that is also turning yellow. I put epsom salt on the bush about a month ago as this was supposed to help with the magnesium problem, alas, the problem persists. The bush is regularly fertilized. I have also treated it with a pesticide. I have looked into watering as a problem, so I started using a moisture monitor to make sure it is not getting too much or not enough water. I don't think it is a lighting problem either. Nothing seems to help!!!!! What is wrong????