Seeing as it is an auto flower, its likely just reached maturity and has started growing some preflowers. I wouldn't start feeding any flowering nutes just yet. Maybe give it another 3-5 days and see how developed the slowers are at that point. I remember it was about 5 or 6 days, from the first signs of pre-flowers, before flowering officially had kicked in. I would feed a very light dose of flowering nutes while maintaining your veg nutes once flowering starts and the stretch begins. During stretch the plant still needs a lot of nitrogen which is why you dont want to completely swap to flowering nutes until it has finished stretching. Might also be a good idea to look up the feeding chart for your nutes and see what it says.