Disclosed are fuel cell architectures, fuel cell stack monitoring systems, and control logic for detecting fluid property changes in a fuel cell stack. A method is disclosed for detecting a flow property change of a fluid in a fuel cell system. This method includes determining, e.g., through system analysis or accessing a look-up table, a correlation between voltage change of the fuel cell systemand flow property of the fluid, and determining, from the voltage-property correlation, a calibrated voltage drop corresponding to the property change of the fluid. The method monitors system voltage(e.g., moving average voltage of the fuel cell stack operating at steady state), and detecting a voltage magnitude change in the system voltage, e.g., when an anode exhaust valve is opened. Responsiveto the voltage magnitude change being greater than the calibrated voltage drop, a signal is generated indicating detection of the flow property change.