Looking good! Usually in 6-8 weeks you can see the pre-flowers with the naked eye (although a magnifier would be recommended for possibly seeing early as possible). Since these are not auto's you don't need to worry about pollen this early since you haven't started the 12-12 yet. I tried to look at your picture but I could not see it well enough to tell yet, but you should be seeing the pre-flowers very soon since you are in week 4 currently.