what is your grow zone?
what is the humidity reading in your environment? indoors and outdoors?
I put my Renanthera plants in mixtures of large coarse mix charcoal, coco chips, lava rock, sponge rock and hydroton in net pots....
I am indoor grower so it is in the southfacing window in the colder months....I put it out of the windowsill when the nights are in the 60's