Flowering Late in Week 3?

Thanks, all! The Autoflower Concentrate that I'm using claims to make the entire operation pretty much water only, but I did get some Build-a-Bloom from BAS. My intent is to add about 1/4 to 1/2 of the recommended amount as a top dress just so that all the nutrients aren't at the bottom of the pot. Based on the advice here, I'll do this prior to my next watering.

4 weeks for an auto flower is quite normal, and flowering is not size influenced, but age determined. This is the problem with auto flowers, they flower no matter what size they are, (even if only a few inches tall), at around the 3-5 week age mark. Cannabis plants still need adequate nitrogen in early flower, it is only later in flower that nitrogen requirements drop off, so don't be too eager to switch to bloom nutrients just yet. What I have been doing for over twenty five years and what I find works extremely well. is to continue with grow nutrients until there are small budlets/tufts of pistils formed, before changing to half grow and half bloom for the next 2 weeks or so, before moving to straight bloom nutrients through until harvest maturity. This seems to produce the biggest flowers on plants that don't completely exhaust themselves and end up a sickly yellow colour by harvest time. Oh yeah, yes, your plant is beginning to enter the flowering phase. Hope this helps, Organoman.

Yep as Roberts said your going into pre flower. That's the problem with autoflower you have no control when it goes into flower.