You don't need strong light to root cuttings (clones). It's a bit of a waste using 250 watts for cloning. The plants aren't growing yet so they don't need that much light. I leave my cuttings on my bedroom floor by the window. Or you can put them on the window ledge or something. You say you have water at the bottom of your propagator, this maybe your problem - the humidity maybe too high. If you soak the rockwool with water then put it in the propagator, it won't dry out because the propagator stops moisture escaping, that's the idea of them. You don't need to fill the bottom of the propagator with water. What is the temperature where your cuttings are? Have you used any nutrients yet?