This is the perfect time to add the nutes... start off slowly, though, to make sure she can tolerate them... Try out 1/4 dose and she how she reacts... The Bruce Banners I've grown have gone into pre-flower quite late for autoflowers so you'll probably have a couple more weeks of veg before she starts sending out signals... and tbh, mine just kind of burst into flower in week 7 so you might want to start introducing bloom nutes about week 5 or 6...
Good luck! And be prepared for unbelievable frost on her!