Can anyone help me figure out what is wrong with my plants?

I was told they are a climbing gardenia but i don’t know the proper names for them. I grew them all from cuttings, and planted them in this bed in the middle of spring last year. Its a raised garden bed, 30cm tall, 30cm deep, plants are spaced roughly 30-40cm apart, on top of clay, filled with a mixture of loose packed 80/20 garden soil and organic fertiliser (purchased from bunnings), and watered as required. There is a black plastic barrier along the fence and deck to stop moisture, but the base is open to the earth. I added some slow release gardenia specific fertiliser about 6 months after they were planted, and i was planning to add some again this month as we’re heading i to spring. They were growing like gangbusters, thick with leaves (you could barely see the fence through the leaf cover) and flowering regularly until about 5 days ago when we had a decent downpour in Brisbane. They have dropped over half of their leaves during and immediately after the rain and aren’t looking too healthy. I tried giving them some seasol tonic thinking they might be a bit too diluted from the rain, but i really have no idea what I’m doing and I’ve gotten lucky up til this point. Help?