you can over fix film, but you need to soak it in the stuff for ages. 10 mins won't be terribly bad for it. 2 hours, maybe.
Different emulsions will need different fixing times. If fixing it for longer removed the milky hue, then that film clearly needs more time to fully penetrate the gelatine and dissolve the unexposed silver. The milkiness is just uncleared silver.
glad you got it sorted.