You could add bonemeal and I usually water 2 times a week in summer and once a week in winter depending on when the medium dries out. They don't like to be extreme dry as the thick leaves suggest. I usually stick my finger in the mix down to about 1.5 inches deep to feel if it is dry.
Thanks for the information. When I look at the young seedlings I do notice a few of then already have the dark purple edge so I suspect the mother plant to be half vinicolor. Hopefully the backcross will be as dark as the ones I had many years ago