Answer: Ficus deltoidea (sometimes sold as F. diversifolia) does normally have those spots on the underside of the leaves. It also typically has a brownish or tannish mottling on the upper surface. Based on your description I am not certain why you are seeing rapid leaf drop, but it might be due to shock at the change in location if you recently purchased it; or it might be due to over watering (allow the soil to become quite dry between waterings.) It might also be related to whatever you used to treat the spider mites, in that plants can react badly to some sprays. You might review the label on the spray you used and see if it is listed for use on Ficus, or not. I'm sorry I can't be more specific for you.
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