I don't remember a drop in form.
Games from last November-December:
Verona 2-2 Juventus
Juventus 3-1 Parma
Milan 1-1 Juventus
Juventus 2-0 Piacenza
Fiorentina 1-1 Juventus
Brescia 0-4 Juventus
11 of 18 is not really a drop in form I wouldn't think.
Of course, Juve lost only 3 all...