Could these white fluffy spots on the wood in my attic be be mold?
I’m 99% sure this is mildew/mold caused by the high humidity level in leaky attic.  Hopefully the moisture levels will come down now that the leak is fixed.
It would be wise to spray the areas with a non chlorine mold killer like Concrobium
For the next few weeks check humidity levels in the attic.  If they remain high you may need to ventilate the attic better.