Most of my trees get what looks like rust spots at the same time that they turn yellow, just before they drop all their leaves and go dormant. I had assumed this was just part of the cycle. I do not water on any schedule. I stick my finger in the soil and only water when the top inch or two get dry. If it is too much water, it is because of rain. I don't really want to cover or move my pots... but should I?
My sister in Hawaii tells me that the leaves on the tree I sent her have also turned rusty lately. I guess I gave her bad info when I told her it is normal this time of year.
If its a deficiency, should I wait until Spring to apply some potassium? I would expect that any balanced fertilizer would have enough potassium to prevent a deficiency.
By the way, here in So. Cal., none of my plants are dormant yet, but some plants have leaves turning yellow (some rusty) and falling off, while at the same time, new leaves are growing. My Panache leaves turned yellow and dropped a week or two ago, and today I see it has a whole new set of leaves top to bottom. Paradise can be confusing.