tops of plants too tall and not producing colas

I have attached some pics here with a few questions. In two I want to figure out why some of my leaves twist and turn and are turning yellow. The others I have simple question. I have a few taller plants than the rest. Even though they are taller, they are not producing the kind of colas that plants lower down are. Would it make sense to just snap the taller ones and lay them down rather than pull them over and kinda block the lower plants. Will it hurt the yield a ton since they don't seem to be producing the same results anyway?

Anyone have any suggestions?

They look fine...if they are developing slowly check for light leaks. DON'T snap the tops off! If anything you can harvest the colas when they're done and let the rest of the plant mature more.

Going into week four of flowering. Do they look like they are developing slow?

what strain? they look nice to me, just need more time. is that light burn on the 2nd photo?

The strain is big bud. Not sure about the light burn. Its been like that since it was much shorter. That's why i posted the pic.

What kind of light are you using?

400 watt HPS

looks like ph issue

looks good to me man. i cant find a thing wrong. but im no expert.