Are they stretching?

I'm a little concerned about the height of my plants. Please refer everything to MY JOURNAL, these are the plants I'm talking about. The strain is Thai X NL but heavy on the Thai side.
I started flowering them when they were 10-12" which happened just after their 3rd week of veg. Now they're just past their 3rd week of flowering and they've tripled in size! The tallest ones are just short of 3ft and the shorter ones are about 6-10" less. The shorter plants were transplanted a week before flowering and the taller ones were transplanted a few days into flowering (reason for height difference).
The light is a 400W HPS conversion bulb in a vented reflector. I keep the the light around 12" from the tops and temps are around 78-80F.
So am I growing x-mas trees here, or is this normal for my strain?
Any help is appreciated, thanks!

Here's a pic that might help, tallest vs shortest (taller plant is 36", shorter is 27").

 

I guess what I should have said is that I'm concerned about the bud's density. Just by looking at it, the one on the left seems like it won't be very dense.

 

It's my first time growing, so patience is a bit of a problem, but I'm working on it, hehe.