My Hot Springs Grandee was installed new in 1996 and other than the occasional fix-it visit by a spa technician, it's been working like a champ for 16 years. This past week we went to use it and found that the water was only around 95 degrees instead of its normal 103. Everything else looks completely normal. Both the red and green lights on the main panel are on, the temperature indicator says 103, pumps all work fine. I drained the spa, cleaned the filters, refilled, and turned everything back on. It heated right up to about 95 degrees and won't get any hotter. One noticeable difference is that the heater return, which normally puts out significant hot water (along with little bubbles) when the thermostat is tripped, now has a pretty anemic flow.
The technician we usually use here in Northern California is booked up for two weeks and we have guests arriving this weekend. Is there a possible simple fix I'm missing, or do I just wait for the technician?