Any Idea What Is Causing This Bud Stretch?

[Bud swelling]

Hi- this is my first grow. I'm growing in Coco under CFL (550w). I'm growing C99 and everything has been going well. I flipped to 12/12 on July 23rd so I'm at the end of week 6 in flower. My buds were forming nicely (I think) until the last week or so when the some buds started sprouting at the top and generally stretching.

I've attached two photos of stretching buds/colas and two photos of the ones that look normal to my newbie eyes.

Many thanks for any help!

 

[Bud swelling]

Are your Nitrogen level's too high for being in flower?
That will do it for sure