Some call these Creeping Charlies, and some don't. Seems to depend on what part of the country you're in. I have a variegated variety. Plectranthus is what this plant is. Many call it Swedish Ivy. Anyway, I had great luck with this plant when I lived in Long Beach, not more than a few miles from the shore. But once I moved inland, I found I couldn't keep them alive! (I love the way they smell, too!)
I tried a few times with no success. Now I have one that is variegated, and it's limping through winter, but doing pretty well compared to my past experiences in a dry climate. I mist it every day, and it has an asparagus fern next to it that gets misted too, and this helps with humidity. The fact though, that you had one in Arizona goes to show humidity may not be as important as we think.
Could yours possibly be variegated? Or is this happening on only a few leaves? I can see where it is more pale on some parts of some leaves, that's why I ask. Mine did get a few black leaves at first too. Mine is very small, in a 3" pot right now, and I sure hope it decides to thrive, because once you have one of these plants, you always want another when you lose it! I hear in some places it's practically a weed.
You say yours gets dappled sun. They don't like a WHOLE LOT of sun, so mine gets just the smallest amount of dappling in late afternoon, because they can and do burn easily. Bright light without direct sun is also favorable for this plant.
