Couple Of Questions, Please Advise...

I'm growing 'Green spirit' a hybrid of skunk and big bud, I'm growing in a mix of rockwool and potting soil using 600w sodiums.
my plants are 5 weeks old (from seed), i have a couple of questions....

2 seem to be well behind the others but i'm not concerned with that but yesterday i had a security problem and my lights went off for about an hour, 2 hours into their 18 hour cycle, would this cause a problem at all?
And secondly and most importnatly 'pinching out', when do i do this? how much do i pinch out and how many times do i do this?
Is there a section on this site about pinching out?
All comments are much appreciated, thanks....

i dont know what pinching out is... same kinda thing happened with me on the lights thou.

i didnt have time to set them up so they went 3 hours without any light from when they had been potted, i mean they should be ok but being interrupted...

they should be ok, i guess the worst that could happen is that they stress out.

sorry i cant help that much as im kind of in the same boat. id wait for some pro's that will prob give u a better answer