What is the ruling on the discharges that come down after lochia (nifas) and menstruation (dawra shahriyyah), and are they considered part of menses or lochia, thereby prohibiting prayer?

Your actions are correct in both instances, because the maximum duration of postpartum bleeding (nifas (definition)) is forty days. Any yellowish or brownish discharge a woman sees during this period is considered nifas. Therefore, your ritual bath (ghusl (definition)) after the forty days is correct. What you saw after that is considered menstruation (hayd), and the maximum duration of menstruation is fifteen days. The yellowish and brownish discharge connected to it is considered hayd. If the bleeding and what is connected to it stops before fifteen days, then all of it is hayd. If it exceeds this duration, then you are experiencing irregular bleeding (istihada).