How's your tap water? You may be just fine with that. If it's soft (under 200 ppm) you could use it after shaking it up with a little pump overnight just to make the chlorine escape. You may not even have enough chlorine in your water to pose a problem. You could even download a water quality report from your local environmental agency that handles the water supply for your area. If the clones look burnt yellow they may be over exposed to light. How many watts is the bulb? If it was an air circulation problem, you would probably see a lot of tiny little spots that resemble spider mite damage (begining of powdery mildew).