They do that in the heat. You can cut them back, but they're going to get leggy again.

So is it best to leave them alone?

cut them back and they just keep going and going. I did it to mine a couple of weeks ago and they are now in a flush of blooms again. They do best in cooler weather but if you keep them well watered and in a spot with a bit of relief from the blazing sun, and cut back the leggy stems, they do great.

How do you cut them, at an angle, just straight or does it matter? How far do you cut back?

I just grab a handful and shear them off under my fist.