Hi there, It looks like the five plants you have listed are all woody shrubs. This means they live from year to year and have woody stems. In my garden I would give all five an application of Osmocote at planting time in the spring. Then the following year evaluate and if the plants are growing, and they are not in pots I would not feed them again as I would not want them growing too fast. I use a mulch on my soil and add compost at planting time so my shrubs do not need extra plant food after the first year. If the plants are growing in containers then I would feed with Osmocote every spring. If leaves are turning yellow on the gardenia it may need a plant food for acid loving plants so  I suggest the Osmocote ARC formula. The letters stand for Azalea, Rhododendron and Camellia food  - all acid loving plants. I do like to keep things simple so I do not use a bunch of different plant foods for different plants. Your next question - Osmocote is not considered an organic plant food but because it is released slowly over time it is very safe to use around pets and all plants. Osmocote is also better to use around water sources or wells as the nutrients will not be released into the water supply as easily as manures or other organic sources of nitrogen. Keep growing, Marianne Binetti