My house was built in 1934 but has mostly been updated. We have one updated bath on the first floor and a new bath on the second floor. My concern is that when I flush the downstairs toilet there is a gurgling noise that seems to be coming from the bathtub. The toilet also has a little trouble flushing sometimes, it hasn't overflowed but it has come close. The upstairs bath seems to be working normally. Any suggestions or is this something to worry over?