Safe pruning?

Hey,indoor,was wondering how much undergrowth trimming can i safely do while its in flowering stage without doing harm?

How many weeks in flower are you?
usually no pruning after 30 days in flower.
need to do your pruning atleast 2 weeks before flower.

they;ve been there over 30 days,just have alot of small under growth and i was thinking if i trim it the energy will go to the rest of the plant growth,but seems to be not safe so ill not do that. i do trim before the flowering stage but i still had alot of small stuff so i was wondering