Your cars are old with high mileage. Unless they’ve been maintained properly, mileage will continue to decrease. There are so many systems on a Prius that aren’t even mentioned in the maintenance schedule. It’s really a crapshoot. The battery needs replacing, or at least reconditioning. The engine is worn, the egr is clogged, the bearings are worn, increasing friction. The intake manifold is clogged, the injectors are clogged, the coils are worn out, the throttle body is worn and dirty, etc. What tires and pressures are you running? There’s an old thread here somewhere, saying that some v’s never got good mileage from new, something about the transmission
