Pre-flower stage timing for auto

This will differentiate greatly by strains. It looks like the majority of the diaries here growing this strain have seen the end of the vegetative cycle coming at weeks 3-4. So you are right on track. If you are noticing a massive growth increase you are now entering flower. I would bet you will start seeing pistols forming in the coming week. My last Auto run all had four weeks of veg before they started flowering. Like you mentioned, it was an explosion of growth once they entered into flower. Time to give it a bit more light and switch to bloom fertilizer. It also looks like the majority of diaries here growing this strain went 10 total weeks so you are nearly halfway to the finish line my friend. I hope this helps.