If you're using preset actions, you have to send a different CC in all of your other presets to change the value back.
For that reason, I don't recommend using preset actions for that purpose. It's much better to use an IA button. Even if it's on a button page you don't access on the PBC, it will send its messages if Send on Preset Change and Update on Preset Change are turned on, and Max Page is set to be equal to or greater than the page number.
For example, create an IA button on page 5, turn on Send on Preset Change and Update on Preset Change. Have the button send the correct CCs to adjust the mix, with the On value set to the higher mix value, and the Off value set to the normal mix value. On the desired preset(s), program the button to turn on. It will send the high mix value on those presets and will send the normal mix value on all other presets.