3rd week flowering are they small

Exactly what Roberts wrote!

Development rate can be different per plant, but It looks liek you have at least 2 more weeks of vege growth remainaing. It may even slowly taper off beyond that. Even the faster 8-week flower varieties out there have robost vege growth for 3 full weeks beyond flip then taper off. So, the guesstimated time the breeder gave for flower can help guesstimate this better, too. Longer flowering plants generally have a longer period of remaining vege growth before it stops in flower. if it's an autoflower, figure "flower" started about 5-7 days before you saw nubs of preflowers growing in order to make it apples-to-apples comparison with photoperiods, which is the context in which I am speaking.

Don't worry about the red leaf stem it's of no concern. It's likely a sun tan from exposure to light or just a general genetic trait. Most Weed displays red leaf stems. Now red stems and stalks, THAT is far more likely to be a Phosphorus deficiency. The why is a whole other rabbit hole.

The red leaf stems indicate a lack of phosphorus, which is important at this stage, and I think your plant stretched too much. The overall dose of fertiliser is probably too low and you should correct it quickly. To compensate for the plant's elongation, you should prune the side branches from the bottom to at least a third of the height: there will never be enough light further down.

I think they look pretty good. Maybe a little hungry for nitrogen but could be the lighting and camera.