It's a bad idea to trim your roots right before you flip your plants to 12/12/flower. As I recently read on ICMAG (and common sense should have told me), the roots don't grow once you put your plants in flower, so here's the tip/trick: allow a week, or two would be better, between trimming the roots and going to flowering mode. If you don't, you'll get like one small bud on the highest node and not much else. Because the root system is pumping as hard as it can, but it's limited by small roots.
Also, as we all know, never touch your plants with your bare hands.