It would help massively if you gave some more information regarding your current set up.
Strain, lights, growing medium and feeding program, area. - all this info will help you get quality advice.
I noticed people have picked up on the red stems and this isn't always a cause for concern as some strains have red stems naturally.
From looking at the pictures you posted your bud development is doing well and you haven't gone too far wrong in my opinion.
Have noticed some cupping on a few leaves which could indicate too hot/too dry but if you have your humidity and temp in check then ignore that. On that note, if you are not familiar with VPD it would be worth learning about it as a lot growers tend not to give it much time but will pay you back in the long run.
As for when flower starts.. personally I would count from the day you flip to 12 12.. but this has been a long running debate for many years and will continue to be. Each to their own I say. But from a scientific point of view, as soon as a plant gets one night of 12 hours, (or there abouts) flowering hormones begin to increase. And this will result in the plants stretching and eventually producing flowers.. each strain will have its own habits which can be affected by the environment.. and to be honest, the only reason it matters when you start counting flowering from is if you are going to run cuts of the same plant again and want to plan time wise. Otherwise, all you need to know is when they are ready. And you do that by looking at the trichromes and the overall appearance.
Hope some of this helps and kudos for trying to improve.
