clones dying..resembles root rot

approximately 50% of my clones die(hydroponics dome usage) . starts in about 1-1/2 weeks after i put them under the dome. i spray using proper ph , reverse osmossis water with some rooter and nutrients(scaled at 1 1/2 tspns per gallon) when successful with some clones(roots grow out approx 2" inside the dome) i put them in the grow room without much better luck. they seem to live approx.2 additional weeks. at the time of transfer they are then exposed to standard growing watering.some prosper and grow nicely while others don't...