Besides the random yellowing and dropping off of leaves and buds, the plant is otherwise putting out new buds and flowers pretty well.
What might be causing this?
The plant is in partial shade (3-4 hours of full direct sun, partial otherwise) and is watered every day. I fertilized and added some new soil few weeks ago, but have been noticing this problem since before that event.
The picture showing the 3 flowers was taken a couple weeks ago, and the other one yesterday.