Hey, autos vegging and flowering time spans differs from one strain to another and they also vary by breeder. Autos usually takes 4 to 6 weeks on average to flip into flowering stage. Usually pistils hairs on the nodes is an indicator that the plants has started flowering. There is also a chance that your plants are photos instead of autos due to unstable genetics. This happened to be the case in my current grow where 2 of my 3 autos turned out to be photos. I let them veg for 6 weeks before I changed their light schedule which kicked the flowering process. Make sure to check the breeder's website to know more about the strain details.