Don't give them tap water at all if you can help it - too many additives like chlorine that will burn the plants. Use distilled water (you can let your water sit out with a large surface area on top for a few days to achieve this). Clones usually have yellowing at the bottom after a few days because, as the new root system begins to grow, the little plants feeds on themselves for food. Finally, I would recommend waiting until the plants have established themselves before adding nutes, similar to seedlings.