Steve,
I don't see anything obviously wrong, so not sure how much help I can be...
In theory, assuming that nothing was scheduled to be running when freeze control kicked in, the system should have tuned on the Pool mode and the pump should have been told to run at 28 GPM. About every 15 minutes, the system should switch over to the Spa mode and then back to the Pool mode.
I have no idea why the pump was running slow.
If this was my pool, I would want to make sure it works the way it should, before it actually gets cold. I suggest that you put your air temp probe in a glass of ice water and see how your freeze control works. Set the system up to the way it would normally be in the early morning, and then make the air temp probe cold and see if the pump comes on at the right speed and that your system switches between the pool mode and spa mode.
If it works great, if not, I seem to remember something about using either all GPM or all RPM. So, if it does not work, you might change the one circuit that you have as RPM to GPM.
Other than that, I've got nothing...
Thanks,
Jim R.