I think that the strong buffer added without dilution could harm the first bacteria it hits, like before it has diluted in the mix. The amount of Orca is small and didn't change the pH of my nutrients when I added it.
It's been a little while since I used Orca but was their suggested mix 0.5 mL per gallon or was it 1.0 mL? I remember a little bit went a long way. As with any liquid Myco/Bennie you should make sure it's not old product, especially if you ordered it online.