will 12/12 screw my babies up?

i have a plant in dirt about 3ft i wanna switch to flower, and some dwc plants a few inches tall. what will happen with the dwc if i switch to 12/12, will they just grow slower? or should i just veg the one in dirt till the dwc is ready to flower also?

the ones in the dwc will flower also i think.if you think that you have the height and room to keep vegging until the dwc plants are ready to flower i would go for that.