Well the first question is how old are they? Usually carnivorous plants can stay active for the first year or 2 after germinating or from leaf pullings. I think you should let the daylight they receive gradually decrease, or use a light to help and leave it off from 12-15 hrs and then when you go into spring, gradually start increasing light from 9 hrs to 15 so they can see the days getting longer and start growing more. giving the plants light cues like increasing or decreasing hours of light, and then giving seasonal cues like less water and cooler temps usually does the trick, although you can put the plants in the fridge if you feel the plants should be going dormant.