Vanda like to be very warm...watered with warm water (they like a mist even better)...and while normal to drop a lower leaf i'm not sure your's looks very healthy. I have seen vanda in large bark with a basket...but not the spagnum. You might want to consider removing it as some of your lower roots look bad. Also; if it has spagnum you should wait to water after the moss is dry. Vandas are also able to handle being fertilized a couple times a week. I use honey in addition to regular orchid fertilizer when they are spiking or sick.