It's ethanol. They're adding more E15 instead of E10 and is reducing mileage by a few percent because the corn has less energy potential.
I highly doubt these suspected 2014 Altima drivers have ever willingly changed an air filter, fuel filter, ran some fuel system cleaner, check their tire pressures religiously, rotated their tires, or used cruise control in their entire lives.
You have a choice. Use more ethanol potent fuels and get worse mileage, or spring for the premium and pay more per gallon.