This is normal for photoperiods, its shows you they are sexually mature and ready to flower when you are.
Nothing to worry about.
You can see on my 8th week of veg my plant was displaying pistils. but I only flipped to flower in week 12.
growdiaries.com/diaries/129773-grow-journal-by-m0use/week/725147
All photoperiod plants need a time to mature, its why when you grow them on 12/12 from seed they don't just automatically enter bloom on the first week, they have to grow up and hit their version of puberty before they can be sexually active. Some plants this is earlier some later all normally within 4-7 weeks. This is not the same as autoflowers though, as soon as you see this on an auto it means it maturing and will be flowering any day.
Good Luck!