Stunted Auto?

My first grow is this autoflower GSC, nearly 4 weeks old.

She seems stunted height wise. About 18cm tall. Lots of the new growth seems to be underneath, coming off lower nodes. But not enough to stretch into light.

Do I need to defoliate? It's my first grow and reluctant. But if the grow at risk.....

Or do I need to repot? It's a 20cm diameter pot. Roots are poking out the bottom, but seems like there is plenty of soil not root bound. Last time I transplanted the shock lasted a couple of days.

Lights too close? I have a 150W CFL and 150W LED (cheap UFO off ebay, I doubt it is actually 150W) about a foot above?

Also I thought it would have flowered by now. Too soon?

OK.
About 3-4 weeks old they hit main veg. They start to branch everywhere. It's normal. All good.

What I can see though, is your plant is definitely filling the pot. Your plant will probably grow 3 times the size, once you hit flower.

It's an auto. So I realise transplant isn't usually a good idea, from what I've heard.
In your case though. I'd beg to differ.
In my opinion transplant carefully to a pot 2-3 times the size.
If you don't, your plant will quickly run out of room. It will give up on lateral growth, and shoot for the sky instead.
You'll end up with a tall, spindly stick. With a few bits of popcorn, extra long nodes, and yellow bottom leaves.

Vote #1 transplant
Don't top, or anything either. Just let autos be.

Looking good for 4 weeks, but I have to agree with Tim. It deffinately needs a bigger pot.