Hi I bought this ficus 2 years ago now and have re potted it once , it was in a 6 inch deep and round pot so I took off some of the bottom roots and re planted it in a pot about 10 inches wide and 4.5 inches deep because I was worried about taking to much root off but now I am wondering should it be in a shallower pot ?

The real issue is shown in the attached pics. There appears to be some brownish spots appearing on some of the leaves bottoms and tops. I have removed all leaves showing these signs. Some leaves are also yellowing/browning then dying and falling off not a lot just some.

Also I see some grey/white stuff along the base of the tree trunk I never noticed this before. Is this something to worry about? Any ideas what it is? Also I sprayed schultz insect spay yesterday as my herbs all had spider mites could this have caused the grey/white stuff? I don't know if it was there before I sprayed it.
The ficus did not appear to have mites but I sprayed it anyway as it was only 3 feet away from the herbs..

Any help would be greatly appreciated thanks.