Are These Pre-flowers?

Hi everybody, well this is my first grow, and it a micro grow. I have 3 plants left ( started with 8 ) and there are about 6 inches tall and around 3 weeks old (maybe a bit more). They are all in 4 inch pots. My biggest strongest looking plant seems to be showing sex. I'm not sure tho, it looks like balls to me =/ but maybe you guys can help me, Thanks in advance! Here are the pictures of what i think to be the sacks.

http://i49.tinypic.com/t7l846.jpg

http://i48.tinypic.com/1eb3i1.jpg