Bad batch of Instant Ocean

[Megalodon]

I did a 25% water change today, with Instant Ocean for the first time, and immediately my tank started crashing! I tested pH (8.2), ammonia (0), nitrite (0), nitrate, phosphate, copper, salinity (1.025), and all looks fine, except for alkalinity... a kH of more than 30!

Both my cleaner shrimp died, my Hawaiian feather duster is laying out of its tube twitching, my Bengaai cardinal is belly up, my royal gramma is missing, and my yellow tang doesn't look impressed. The water is also very cloudy white.

Normally I use Red Sea but decided to switch to IO. The new water was RO and mixed for 24 hours with a powerhead, but I added a bit of salt 30 minutes before to adjust salinity. The water was introduced slowly over two hours.

I thought it could have been the RO but it tests fine. I did another batch this time with tap water and mixed it vigorously for 30 minutes. It tested the alkalinity at over 37!

I brought it back to JL Aquatics today and they did a test batch and their test kit showed kH off the scale too. They were shocked, but told me it was because the water had to mix for 24 hours, there has never been a problem with IO ever, and they just gave me a new bucket.

The new batch I'm doing right now with tap water has an alkalinity of only 5, so obviously there had to of been something wrong with the first bucket of IO. This batch also isn't so cloudy.

Does anyone know what could of happened? Anyone had a problem with IO lately?