I've got a small setup with 4 Big Bang feminized autoflowers. They've been growing strong for about 3,5 weeks now, stand 6 inches tall (but quite bushy) and I give them vegetative nutes 2 x week on an 18/6 light schedule (400W). They're a little fragrant already but no signs of flowers. I know they start flowering when they decide they are "big enough", but how do I know when to switch to flowering nutrients?
When you start to see white hairs forming into tiny buds, introduce small anounts of flowering feed working up to a stronger mix by week 4,5 of flowering. Usually from what I have see the Autos will veg/grow for 3-4 weeks then start to make the transition to flowering. GooD LucK