Yellow leaves occur from overwatering your pothos. They can also in some cases be from underwatering. Check the soil and you'll know which one it is, and in either case, check the soil ever week and only water it if almost dry. This way you'll avoid over and underwatering. You can cut off the leaves that are yellowing. It is also a good idea at this point from the healthier parts of the plants in case the root rot is fatal.