I have about 30 gallons of mix water churning on the patio. The KH is kinda high (15) and the pH is kinda low (7.9).

In the main tank, KH is 9 and pH is 8.4.

How concerned should I be?

When I mix the water I always add salt, wait a few days, add buffer, wait a few days, test it to be sure, and then do the water change. It's always been right on before... but this time I had the bright idea to clean the hose.

It was getting icky and I'm cheap, so I soaked it in vinegar for a few days to get off the gunk. It worked quite well. I thought I rinsed it well enough, but apparently not. That's the only thing different in the routine, so it had to have caused the pH drop, right?

If I'm too cheap to buy a new hose I'm certainly too cheap to dump 30 gallons. Should I try fixing it or not worry about it? I'd be using this mix over a 6 week period, doing 10g every 2 weeks in a 90.