Ficus benjamina 'White Spot' Problem
i have a (rather large) Ficus benjamina and for the last 2 weeks it has started to drop leafs. Some were yellow/brown but now it even starts to drop green leafs.
As i picked up the leafs i noticed that they all had exactly one white spot at the backside base of leaf (where the stem turns into the leaf).
The spot is 3 dimensional sort of white opaque and wax like. It can be removed quite easily by a slight touch. I am very certain that it is not a cocoon of any kind (no web/silk like substance).
What is peculiar (as i mentioned before) is that there is always exactly one spot in exactly the same place on the affected leafs. These spots are not located anywhere else on the leaf or any other part of the plant.
Since the problem started i also notice that the plant uses much less water, normally i have to use a full can every 2-3 days, but now it has been 4 days it has used almost nothing so i am really worried here. (it is one of those lime pebble pots with water indicator)
I searched on this forum and elsewhere on the web but the only thing i saw on one forum was that this might be a plant secretion used to 'cool down' the plant/leaf when it is too warm. This sort of seems reasonable since i have turned up the heat since i felt sort of sick, but i don't think the room temperature is ever above 85 F. The air however is very dry (no humidifier).
Also (should it matter), every 2 weeks a use a bit (1 tee spoon to 1 can of water which is about 1/3 of a gallon) of universal mineral fertilizer (Magnesium and Sulfur). Could it be that as well, i mean maybe i shouldn't fertilizer in winter or maybe it is too much? I mean i have not seen the typical signs for 'too much fertilizer' but maybe it is a contributing factor to this problem?
I just want to be sure i am doing the right thing since i really like this plant.
Thanks for any info/help.