Newbie 1st grow needs advice

Thread starter #1
I have 3 plants in a hydroponic setup.
All 3 are from seed, problem is one plant has become larger than the other 2 by a long way and is in danger of shrouding the light from it's neighbour.
They are all Trainwreck strain and in week 6 of grow with 20/4 hours light/dark.
How can I either slow the larger plant or bring the smaller plants on. Is this even necessary?