I am a newbie.
As others say you may pull light up just a little bit, maybe 2-3cm because I think your plants showing very lite light stress, but don’t worry about them being short.
They will become much taller when they enter pre flowering stage.
My plant grew 40cm taller in 16 days.
1. Either your light is hanging too low and they're not stretching.
2. You've taken pots that are too wide, so they're growing more outwards than upwards.
3. By tying them down, you're preventing upward growth.
Good luck!