I should have been more clear, so I will double check. Do you mist them with water? If so, is it treated water? I ask because sometimes my tap water will leave white residue on leaves. It has some mineral content which doesn't evaporate and leaves the whitish coating. I'm not sure why my water doesn't do it all the time. I suspect the water treatment plant isn't always consistent, but I don't know. I do grow Achimenes and Eucodonias, but only outside in the summer and they are remarkably pest free plants.
