This summer I had to run my pump for 15 hours and have my SWG output set to 80% to maintain proper FC 5ppm for my CYA of 80.

Does that amount of pump time and % seem out of the ordinary?

Background about my pool: The pool is not quite one year old. Swim load is on the heavier side for a residential pool. Wife taught private lessons 7 hours a day plus family and friends use everyday. Pool is in full sun, but we were mainly in the upper 70's all summer. We had a handful of days in the 90's. The pool temp was 85-90 degrees all summer with the solar heating.

Lately our temps have dropped and the pool is now running 80-85 degrees and our FC is running too high. It rose to 17ppm from 5ppm in two days. I turned off the SWG and let FC drop to 7ppm. I then set the pump run time to 10 hours and turned the SWG to 20%. I let this run for one day and checked my FC yesterday and it was 12ppm. I turned off the SWG again last night and will let the FC lower. We still use the pool everyday but the lessons have stopped.

I have removed the SWG to look for scaling but have found it to be clean every time. My last check was 2 weeks ago.

With this info does it seem like my SWG is behaving reasonably or is something acting up?

FC 12
TC 12
PH 7.6
TA 100
CH 270
CYA 80
SALT 3200
BORATES 45ish not quite 50

I did have nascent algae at the beginning of spring but with the help reading this forum I fixed my water and have had no problems all summer. The Chlorine/CYA Chart in pool school was the key to my success.
Thank you.

I'll place the blame for your high demand earlier in the season squarely on those swimming lessons. High bather load (especially little kids) = lots of pee in the pool = really high FC consumption. What you've seen recently sounds normal to me.