Off hand I don't know, but I do know they list the phospherous content on the boxes and bottles of automatic dishwasher detergent. Just take a look at them next time you are shopping.
We have hard water as well and the ONLY dishwasher detergent that was high enough was cascade, no store brand came close, we checked.
Perhaps to be safe, warranty and otherwise, you should contact Whirlpool ... This link has a 'search' tool and a contact link:
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