Hello, I have a Aber/Pacific tub with a separate circulator for the heater. I changed the water a couple of days ago, heated up as normal. Two days later the temperature dropped from 101 to 90. If I run the 2 main pumps the water will raise a couple of degrees then go back to around 90 in an hour. The control indicates that it is calling for heat each time I check. This unit also has a pressure switch in clear tubing so you can clearly see that there is sufficient flow through the heater with only the small circulator running. I am stumped on this one, any help would be greatly appreciated.