Plant growth seized

Me and a friend both planted same strain seeds at the same time, roughly same conditions (same pots, soil, light etc). Both are in the same place in different houses so that they both recieve roughly the same light etc. However, mine appears to have stopped growing, there are no signs of abnormality (all the leaves are green and healthy, the stem is fine) but my friends plant has grown to almost triple the size of mine.

What is happening here?

Pics ? Could just be different phenotypes, Could also be down to other things tho,

I think I found the problem with my plant, when checking the roots I found that they had become far too big for the plant, and were coming out the bottom of the pot, I put the plant into a pot 3x as big but some of the roots snapped in the process, i'm hoping this doesn't do much damage.. This still doesn't explain why my friends plant grew alot taller in the same size pot though.

shit happen if u want my opignions go straight from Jiffy pellet or any smallish container to a giant one it avoid alot of stressful moment get a 5 gal and u will have nough root for a 1/2 pounder