"Well, it could go either way. One, someone is sabotaging your wells, trying to discredit you and killing a bunch of people they don't like. Or two, through some oversight from you, some of your wells are deteriorating to the point that the disease flourished and spread. Which one sounds most likely to you?"
Sora puts that out there with a more 'matter of fact' tone to help everyone come to the same conclusion.

Spoiler: Diplomacy Check
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(1d20+14)[32]