16 dKH is really high, you want between 8-12. Have you started a new bucket of salt and/or done some large water changes in the past 2 weeks? I agree that your Ca shouldn't be maintaining at 480 with that Alk reading.
I find these neon GSPs to be my Canary in the Coalmine, if params start to go wonky they're the first to show me...
HOLD it a minute - have you been using that Liquid Reactor stuff?
Just curious.