Paphs. like to be moist but they do not need as much water a your phrags -that will encourage root rot. When you water make sure that they are fairly dry before you water again. Give them a weak solution of balanced fert weekly. The yellowing leaf is normal, the older leaves always go yellow when they are of no more use to the plant. They like to be fairly warm -room temperature, and they need good humidity, spraying once twice a day will be fine. As your roots were bad, I would just spray the medium when it appears to be dry until the new roots are long enough to manage being soaked. Good luck with it. Paphs are extremely addictive and before you know it you will have ten or more!