They might just be too cold. Make sure that they are between 70 and 80 degrees F (whatever C that is), and if need be you can just start them in soil under a light to keep them warm, but in this case don't let them get too warm, try to stay in that 70 to 80 degree range. You may also want to invest in a Germination Station, it's got a heat mat, or a heat mat and a Sunleaves Float and Grow. Or just get Sunleaves plugs for the float and grow and put the plugs in soil, water plentifully, and put under a warm light or just let them sit in a warm room.