I have a Chandleri Elegans Variegated in the yard of a 40-year old house that I moved into a few months ago. It is blooming nicely, and generally looks in good health, but I noticed that some of the leaves have a bright yellow variegation, similar to that found on some house plants. It doesn't look like a typical nutrient deficiency (I have a degree in soil microbiology), but is more of an irregular blotchy pattern. Any suggestions as to what may cause this? Is it possibly a virus?