Howdy new,

You should be just fine,it's when they've been in the dark for a hour or more,that it would cause problems.

I think 'light poisoning',is when you have too much light,too close to the plants..or not too close,just too much light..it can overwhelm the plants,if you git too much intensity per square foot,like over 50 watts per .

I may be totally wrong..if I am..by all means,someone please correct me

Have a good one...