Thanks for all the posts and replies. I have been watching closely both the heard and the numbers. Ph has been super stable at 7.2. I have checked several times a day, though I have missed some checks.
It's been a while and the rest seem to behave normally. We have had a run of unusually sunny and warm weather for the pacific north west. As a result pond temps have been higher than typical for me (upper 60's) though still cold for most.
Given the couple of maybe's for Costia I am going to go ahead and treat the pond. I can redirect the incoming water for the treatment.