Lights To Close?

Hi everyone, wondering if I could get some opinions on this.
I am currently running 2 600W HPS lights and my plants are getting a little to tall in my room.. Lights are maxed out to the top, and the top of the buds are only about 18" form the hood..So far no signs of burns or curling leaves.
but I was wondering will this hurt my yield or potency of the final grow?

Also my temps are 86-84 lights on and 70-68 lights off..

And I am about to enter my 3rd week of flowering, and can I still trim off the branches on the bottom so the light can focus on the top... but leave the fan leaves alone?

Thanks everyone...

put your hand between the light and the plant... move it closer to the light until it just starts to feel warm... dont let the tips get much closer than this point... tie them down a little bit if you have to