help in Hydro RDWC/DWC

Your ppms aren't that high. When your plants display your traditional "overwatered" look in hydro it typically means your not running enough oxygen in your reservoir or you're keeping your reservoir too full and the plant base is staying too wet. In a top feed recirculating system I suspect the later being more the issue. Once you have roots emerged, the recirculating is pointless. It's honestly overkill even earlier, just the humid environment inside the reservoir is enough to promote root growth. If your roots are brown you're also likely developing root rot unless it's staining.