I have 2 blue widows in the 4th week of flower and the bud growth is like yours. Be patient, that's all you can do. My plants have small buds BUT, when the growth stopped, the trich production kicked into gear. I have small buds covered in trichs now, and still 4 weeks minimum to go! They say the buds put on 25% of their weight in the last 2 weeks, and my autoflower plant proved that to me.