Do i have to trim my plants?

I vegged my 6 Super skunk clones for 3 weeks and they are now in 3rd week of flowering in a bud box under a 600w HPS, I have not trimmed any leaves of so far, do i have to trim the plant to allow more light to the bottom?

I am new to growing so as much advice as possible would be great

Peace

you can if you want. But the plant will kill off leafs it doesn't need due to lack of light anyway.