9.3 is quite high. You should try to keep it around 8.5, highest.
Baking soda stops dissolving in that range, so that shouldn't be
kicking it up over 9. Have you put any objects in the pond recently?
Any cement blocks or something like that? That will raise your PH
through the roof.

If your PH stays up in the 9s or higher, you'll run into Alkalosis,
which can cause big losses. You'll notice that the fish get
excessively slimy and are gasping at the surface if that happens, and
you won't have much time to get things right, starting with a major
water change.

If it were me, I'd avoid the CACL2 and baking soda at least until you
get this worked out. It will only make the problem harder to diagnose.
The PH is likely to be a much worse problem for your fish than GH/KH
levels.

Dave