Re-pot in bigger pots, make sure the soil has alot of perlite.

In answer to your Q the plants will normally show preflowers on a vegative light cycle, but they need to be alot older than those plants. They wont bud though on vegative light cycle unless they are ruderalis. (Auto-flowering strains)

Put the lights on 12/12 when you want to bud the plants.

The smaller ones look like they are streching for the light, move it closer to avoid this.

Make sure the light doesnt burn the bigger one though.