I am a newbie here, my fig trees (and my home) are in Savannah, GA, right now I am sitting at my folks house in Germany, researching figs, anxious to get back into my garden at the end of August! :)
I had the same thing occur on my (very) old, in-ground trees last year, where big patches of leaves turned the way yours did. By the end of summer my trees had partially defoliated.
I was told it was fig rust, this year I treated both trees with a fungicide (copper solution) early in the season, and so far only very few leaves have been affected.
Hope your leaf problem turns out to be a passing occurrence!