The Crystal Conspiracy

Due to the extreme levels of pollution brought to the surface during the Blight Tide, Kunrai's citizens have developed sophisticated methods of determining whether their food or water is fit for consumption during this time of year. The most common, and affordable, detection methods involve alchemically treated crystals available for sale in most common markets. When touched to food or drink, these crystals light red if toxins are found, or green if the meal is fit for consumption. More advanced crystals provide more nuanced information, and the most powerful can identify adulterants in a meal.
For the most part, the people of Kunrai understand and trust these crystals to keep them safe during one of the most dangerous times of year. Though crystals can be expensive, even the bargain models provide a level of security that was previously unknown within the drowning city. This has saved countless lives over the years, and is regarded as a worthy expense.
Recently, however, rumors have begun to spread that the alchemists who provide the crystals have been making subtle, but deadly, changes to their contraptions. Some claim there are crystals with reversed colors. Others believe that rival alchemist guilds are using the crystals to wage a proxy war between neighborhoods. Though no one can provide concrete proof that the crystals are unreliable, the rumors have taken on a life of their own.
While the nobility is loathe to become involved in the petty concerns of the citizenry, this conspiracy theory may force their hand. While there is no proof that the crystals have caused any deaths, or even illnesses, during the last Blight Tide, this misinformation could cause havoc during the next one. If citizens refused to test their food, or believed the crystals were reversed, the effects would be devastating. Hundreds, if not thousands, or preventable deaths would cause horrible chaos in Kunrai, endangering public welfare and security.
Nobles would certainly pay very well for concrete proof that the crystals are still reliable, and would likely pay even more for information leading to the source of this dangerous campaign of whispers.