Thanks for the replies.
I don't have a temp guage so can't measure, but the water is alot cooler now, and being a small pond, the variation would also be greater during the day.
There is some clamping of the fins, but only when they park and they also tend to park in sunnier spots in the pond.
I've also noticed that their eating is slowing down, and I find that I am feeding half of what they would normally get down within 10 minutes.
I'll keep an eye on the clamping, but what woudl this mean?
Thanks again