Any ideas on the rust-like browning on the leaves of my ZZ plant? I always wait until he’s completely dry before watering. He is currently moist from about an inch below the surface all the way down, so he won’t need watering for awhile. Over the last couple of months, I’ve had a few stems where all the leaves turned yellow. In fact, the leaves are turning yellow on a stem right next to this one. The rest of the plant is beautiful and pumping out new growth constantly. He sits on a dresser in my bedroom that is about 6ft. from the intake vent. This is the only thing that I can think of that would be affecting the plant. I’ve never seen these reddish brown spots on a plant before, so I’m hoping someone can give me guidance.