In any case though this is a good lesson to be taught , always test your first (even last cup) in a bucket or box , bad salts are an easy possibility and they happen all the time so don't trust salt mixes , the other being always verify things with a different test/type .
Fwiw a ph reading of 9 would be fatal to the animals and would be very hard to achieve , the same can be said for very very low readings.....when these appear something is a miss and it's usually the testing error
I would Test your Alk levels now as well to just to be on the safe side
Good luck man a bad batch of salt would have been way harder to resolve as you don't always know what in the salt is doing the damage , equipment failures start you in the right direction right away